PCI interface in a computer: types and purpose. A photo

Currently, in the field of complex electronics, there is an active and rapid introduction of new technologies, as a result of which some components of the system may become obsolete and cannot be updated, etc.

In this regard, it is necessary to connect various add-ons to them and, for which certain adapters are often required.

In this article, we will look at the pci-e pci adapter, how it works and what features it has.

Definition

What is this device and what is it for? Strictly speaking, this is an input and output bus that connects to a personal computer.

To this bus itself, that is, to the adapter, you can connect a certain (different depending on the configuration) number of external peripheral devices.

A serial connection connects these peripherals to a computer.

The main characteristic of such a device is its throughput.

It is she who characterizes (in the general case) the quality of work, its speed and the speed of the computer and the elements connected in this way.

The throughput characteristic is expressed in the number of connection lines (from 1 to 32).

Depending on this basic characteristic, the price of this device can also vary significantly. That is, the better this characteristic is (the indicator is higher), the higher the cost of such a device. In addition, much depends on the status of the manufacturer, the reliability of the equipment and its durability. On average, the price starts from 250-500 rubles (for Asian products with low bandwidth), up to 2000 rubles (for European and Japanese devices with high bandwidth).

Specifications

From a technical point of view, such a device has three components:

Above it was written about the exceptional importance of the bandwidth of the device for its normal functioning.

What is throughput? To answer this question, you need to understand the principle of operation of such an adapter.

It is capable of simultaneous bi-directional (card-to-peripheral and peripheral-to-card) equipment connection.

In this case, data transmission can occur both over one or several lines.

The more such lines, the more stable the device works, the higher its bandwidth and the faster the peripheral equipment will be.

Important! Depending on the number of lines, the device can have different configurations: x1, x2, x4, x8, x12, x16, x32. The figure indicates directly the number of lanes for two-way simultaneous transmission of information. Each of these strips consists of two pairs of wires (for transmission in two directions).

As can be seen from the description, this configuration significantly affects the cost of the device.

But what practical significance does it have, does it really make sense to spend extra when buying a device?

It directly depends on how many you plan to connect to the motherboard - the more there are, the more bandwidth the device needs to keep the computer stable.

Encryption

With such a system of information transmission, a specific system is used to protect it from distortion and loss.

This protection method is designated 8V/10V.

The point is that in order to transmit 8 bits of necessary information, an additional 2 service bits must be used to implement security and protection against distortion.

When such an adapter is used, 20% of service information is constantly transmitted to the computer, which does not carry any load and is not needed by the user. But it is she who, although it loads (however, very slightly), ensures the stability of the bus and peripheral devices.

Story

In the early 2000s, the AGP expansion slot was actively used, it was with its help that .

But, at some point, its maximum technically possible performance was achieved and it became necessary to create an adapter of a new type.

And soon PCI-E appeared - it was 2002.

Immediately there was a need for an adapter that would allow you to install new graphics solutions in an outdated expansion slot or vice versa.

Therefore, in 2002, many developers and manufacturers began to seriously create such an adapter.

At that time, the device had one important quality - the ability to upgrade a PC by spending minimal amounts on it, because instead of replacing the motherboard, a relatively inexpensive adapter was enough.

But the development was not successful, because at that time they cost almost the same as the first adapters, and therefore it became necessary to develop a simpler adapter configuration.

Interestingly, manufacturers have also consistently increased the throughput of such devices. If for the first configurations it was no more than 8 Gb / s, then for the second it was already 16 Gb / s, and for the third - 64 Gb / s. This met the requirements of increasing loads arising from the modernization of peripheral devices.

At the same time, slots with different transfer rates are compatible with any devices of a lower "speed" level.

That is, if you connect a second or first generation graphics platform to the third generation slot, the slot will automatically switch to a different speed mode corresponding to the connected device.

Differences between PCI and PCI-E

What are the specific differences between these two configurations?

In terms of its technical and operational characteristics, PCI is similar to AGP, while PCI-E is a fundamentally new development.

Whereas PCI provides parallel transmission of information, PCI-E - serial, due to which a significantly higher information transfer rate and performance are achieved even with the use of an adapter.

Why is it needed?

Why is such an adapter needed and what can it be used for, is it possible to do without it?

It must be understood that most users do without this equipment because it is not necessary even on old computers subject to significant wear and tear.

This is additional equipment, which in some cases will improve the functionality of your PC, but without which an ordinary user can do without.

In fact, the use of such an adapter gives only one main advantage - the ability to connect a certain number of peripheral devices to the memory card, while it is impossible to connect so many of them directly. For example, in this way you can connect a discrete video or in addition to the main one.

Also, a fairly convenient feature can be the simultaneous quick shutdown of all peripheral devices if necessary.

For example, in the case when the computer performance decreases or for other reasons. In this case, the user does not need to programmatically disable components for a long time.

Disadvantages and possible problems

There are a number of significant disadvantages of these devices, and problems that they can cause during operation.

Most often, there are the following difficulties:

• The device is quite large, because it does not always fit in miniature ones;
• The second point automatically follows from the first point - the adapter is not designed to work with laptops;
• Stable operation of many devices is only possible in combination with low-profile cards;
• There is always a possibility of a failure, software or technical (minor) incompatibility of the device with the motherboard of your PC (everything is complicated by the fact that most of these devices are declared universal, although they actually work with many less stable than with others);
• Some amounts of PC RAM are constantly occupied due to.

If there is a need to connect to the motherboard additional devices, then it makes sense to try this method. But you need to remember that normal stable operation is possible only with a high-quality and productive motherboard and peripheral device.

In the past, the mainstream consumer was mainly interested in two types of SSDs: either high-speed premium models like the Samsung 850 PRO, or value-for-money offerings like the Crucial BX100 or SanDisk Ultra II. That is, the segmentation of the SSD market was extremely weak, and although competition between manufacturers unfolded in the areas of performance and price, the gap between top-end and bottom-end solutions remained fairly small. This state of affairs was partly due to the fact that SSD technology itself significantly improves the user experience of working with a computer, and therefore implementation issues fade into the background for many. For the same reason, consumer SSDs have been incorporated into the old infrastructure, which initially focused on mechanical hard drives. This greatly facilitated their implementation, however, concluded the SSD in a rather narrow framework, which in many respects hinders both the growth in throughput and the reduction in the latency of the disk subsystem.

But until a certain time, this state of affairs suited everyone. SSD technology was new, and users moving to SSDs were happy with their purchase, even though they were essentially getting products that didn't actually perform at their best, and their performance was held back by artificial barriers. However, to date, SSD, perhaps, can already be considered the real mainstream. Any self-respecting owner of a personal computer, if he does not have at least one SSD in his system, is very serious about acquiring it in the very near future. And under these conditions, manufacturers are simply forced to think about finally deploying full-fledged competition: destroying all barriers and moving on to producing wider product lines that fundamentally differ in their proposed characteristics. Fortunately, all the necessary ground has been prepared for this, and, first of all, most SSD developers have the desire and opportunity to start releasing products that work not through a legacy SATA interface, but through a much more efficient PCI Express bus.

Since SATA bandwidth is limited to 6 Gb/s, the maximum speed of the flagship SATA SSDs does not exceed 500 MB/s. However, today's flash-based drives are capable of much more: after all, if you think about it, they have more in common with system memory than with mechanical hard drives. As for the PCI Express bus, it is now actively used as a transport layer when connecting graphics cards and other additional controllers that need high-speed data exchange, such as Thunderbolt. One PCI Express Gen 2 lane delivers up to 500 MB/s of bandwidth, while a PCI Express 3.0 lane can reach speeds of up to 985 MB/s. Thus, an interface card installed in a PCIe x4 slot (with four lanes) can exchange data at speeds up to 2 GB / s in the case of PCI Express 2.0 and up to almost 4 GB / s when using PCI Express third generation. These are excellent indicators, which are quite suitable for modern solid-state drives.

From what has been said, it naturally follows that in addition to SATA SSDs, high-speed drives using the PCI Express bus should gradually find distribution on the market. And it really is happening. In stores, you can find several models of consumer SSDs from leading manufacturers, made in the form of expansion cards or M.2 cards that use different variants of the PCI Express bus. We decided to put them together and compare them in terms of performance and other parameters.

Test participants

Intel SSD 750 400 GB

In the SSD market, Intel follows a rather non-standard strategy and does not pay too much attention to the development of SSDs for the consumer segment, concentrating on server products. However, its proposals do not become uninteresting, especially when it comes to a solid-state drive for the PCI Express bus. In this case, Intel decided to adapt its most advanced server platform for use in a high-performance client SSD. This is how the Intel SSD 750 400 GB was born, which received not only impressive performance characteristics and a number of server-level technologies that are responsible for reliability, but also support for the newfangled NVMe interface, about which a few words should be said separately.

If we talk about specific improvements to NVMe, then the reduction in overhead costs deserves mention first of all. For example, transferring the most typical 4-kilobyte blocks in the new protocol requires only one command instead of two. And the entire set of control instructions has been simplified so much that their processing at the driver level reduces the processor load and the resulting delays by at least half. The second important innovation is support for deep pipelining and multitasking, which consists in the ability to create multiple request queues in parallel instead of the previously existing single queue for 32 commands. The NVMe interface protocol is capable of serving up to 65536 queues, and each of them can contain up to 65536 commands. In fact, any restrictions are eliminated at all, and this is very important for server environments, where a huge amount of simultaneous I / O operations can be assigned to the disk subsystem.

But despite working through the NVMe interface, the Intel SSD 750 is still not a server, but a consumer drive. Yes, almost the same hardware platform as in this drive is used in server-class SSDs Intel DC P3500, P3600 and P3700, but the Intel SSD 750 uses a cheaper ordinary MLC NAND, and besides, the firmware is modified. The manufacturer believes that thanks to these changes, the resulting product will appeal to enthusiasts, as it combines high power, a fundamentally new NVMe interface and not too intimidating cost.

The Intel SSD 750 is a half-height PCIe x4 card that can use four 3.0 lanes and achieve sequential transfer rates up to 2.4 GB/s and random operations up to 440K IOPS. True, the most capacious modification of 1.2 TB is the most productive, while the 400 GB version we received for tests is a little slower.

The drive board is completely covered with armor. On the front side, this is an aluminum heatsink, and on the reverse side, there is a decorative metal plate that does not actually come into contact with the microcircuits. It should be noted that the use of a radiator here is a necessity. The main controller of the Intel SSD generates a lot of heat, and at high load, even a drive equipped with such cooling can warm up to temperatures of the order of 50-55 degrees. But thanks to the pre-installed cooling, there is no hint of throttling - performance remains constant even during continuous and intensive use.

The Intel SSD 750 is based on the Intel CH29AE41AB0 server-level controller, which operates at a frequency of 400 MHz and has eighteen (!) Channels for connecting flash memory. Considering that most consumer SSD controllers have either eight or four channels, it becomes clear that the Intel SSD 750 can actually pump significantly more data over the bus than conventional SSD models.

As for the flash memory used, the Intel SSD 750 does not innovate in this area. It is based on the usual Intel-made MLC NAND, released according to the 20-nm process technology and having both 64 and 128 Gb cores interspersed. It should be noted that most other SSD manufacturers abandoned such memory a long time ago, switching to chips made according to thinner standards. And Intel itself has begun transferring not only its consumer, but also server drives to 16-nm memory. However, despite all this, the Intel SSD 750 uses older memory, which supposedly has a higher resource.

The server origin of the Intel SSD 750 can also be traced in the fact that the total flash memory capacity of this SSD is 480 GiB, of which only about 78 percent is available to the user. The rest is allocated to the replacement fund, garbage collection and data protection technologies. The Intel SSD 750 implements the traditional flagship RAID 5-like scheme at the level of MLC NAND chips, which allows you to successfully restore data even if one of the chips completely fails. In addition, the Intel SSD provides complete data protection from power outages. The Intel SSD 750 has two electrolytic capacitors, and their capacity is enough for a regular shutdown of the drive in offline mode.

Kingston HyperX Predator 480 GB

Kingston HyperX Predator is a much more traditional solution compared to the Intel SSD 750. Firstly, it works through the AHCI protocol, not NVMe, and secondly, this SSD requires the more common PCI Express 2.0 bus to connect to the system. All this makes the Kingston version somewhat slower - peak speeds for sequential operations do not exceed 1400 MB / s, and random ones - 160 thousand IOPS. But HyperX Predator does not impose any special requirements on the system - it is compatible with any, including old platforms.

Along with this, the drive has a not quite simple two-component design. The SSD itself is an M.2 form factor board, which is supplemented with a PCI Express adapter that allows you to connect M.2 drives through regular full-size PCIe slots. The adapter is made in the form of a half-height PCIe x4 card that uses all four PCI Express lanes. Thanks to this design, Kingston sells its HyperX Predator in two versions: as a PCIe SSD for desktops and as an M.2 drive for mobile systems (in this case, an adapter is not included in the delivery).

Kingston HyperX Predator is based on the Marvell Altaplus controller (88SS9293), which, on the one hand, supports four PCI Express 2.0 lanes, and on the other hand, has eight channels for connecting flash memory. This is Marvell's fastest mass-produced PCI Express SSD controller to date. However, Marvell will soon have faster followers with support for NVMe and PCI Express 3.0, which the Altaplus chip does not have.

Since Kingston itself does not produce controllers or memory, assembling its SSDs from the element base purchased from other manufacturers, there is nothing strange in the fact that the HyperX Predator PCIe SSD is based not only on a third-party controller, but also on 128-gigabit 19- nm MLC NAND chips from Toshiba. Such memory has a low purchase price and is now installed in many products of Kingston (and other companies), and primarily in consumer models.

However, the use of such memory has created a paradox: despite the fact that, according to its formal positioning, the Kingston HyperX Predator PCIe SSD is a premium product, it only has a three-year warranty, and the stated mean time between failures is much less than that of the flagship SATA SSDs. other manufacturers.

No special data protection technologies are provided in Kingston HyperX Predator either. But the drive has a relatively large area hidden from the user's eyes, the size of which is 13 percent of the total capacity of the drive. The spare flash memory included in it is used for garbage collection and wear leveling, but is primarily spent on replacing failed memory cells.

It only remains to add that the HyperX Predator design does not provide any special means for removing heat from the controller. Unlike most other high-performance solutions, this drive does not have a heatsink. However, this SSD is not prone to overheating at all - its maximum heat dissipation is only slightly higher than 8 watts.

OCZ Revodrive 350 480 GB

The OCZ Revodrive 350 is rightfully one of the oldest consumer PCI Express SSDs. Back in the days when no other manufacturer even thought about releasing client PCIe SSDs, OCZ had the RevoDrive 3 (X2) in its lineup, the prototype of the modern Revodrive 350. However, the OCZ PCIe drive's lingering roots make it a somewhat strange proposal. against the background of current competitors. While most manufacturers of high-performance PC drives use modern controllers with native support for the PCI Express bus, the Revodrive 350 has a very intricate and clearly suboptimal architecture. It is based on two or four (depending on the volume) SandForce SF-2200 controllers, which are assembled in a zero-level RAID array.

If we talk about the 480 GB OCZ Revodrive 350 model that took part in this test, then it is actually based on four SATA SSDs with a capacity of 120 GB each, each of which is based on its own SF-2282 chip (an analogue of the widespread SF-2281) . Then these elements are combined into a single four-component RAID 0 array. However, for this purpose, a not quite familiar RAID controller is used, but a proprietary virtualization processor (VCA 2.0) OCZ ICT-0262. However, it is very similar to the fact that this name hides a flipped Marvell 88SE9548 chip, which is a four-port SAS / SATA 6 Gb / s RAID controller with a PCI Express 2.0 x8 interface. But even so, the OCZ engineers wrote their own firmware and driver for this controller.

The uniqueness of the software component of RevoDrive 350 lies in the fact that it does not implement quite a classic RAID 0, but some kind of it with interactive load balancing. Instead of splitting the data stream into blocks of a fixed size and sequentially transferring them to different SF-2282 controllers, VCA 2.0 technology involves the analysis and flexible redistribution of I / O operations depending on the current occupancy of the flash memory controllers. Therefore, the RevoDrive 350 looks like a solid state drive to the user. You can’t enter its BIOS, and it’s impossible to find out that a RAID array is hidden in the bowels of this SSD without a detailed acquaintance with the hardware stuffing. What's more, unlike conventional RAID arrays, RevoDrive 350 supports all typical SSD features: SMART monitoring, TRIM and Secure Erase.

RevoDrive 350 is available as boards with PCI Express 2.0 x8 interface. Despite the fact that all eight lines of the interface are actually used, the declared performance indicators are noticeably lower than their total theoretical throughput. The maximum speed of sequential operations is limited to 1800 MB / s, and the performance of arbitrary operations does not exceed 140 thousand IOPS.

It's worth noting that the OCZ RevoDrive 350 is a full-height PCI Express x8 board, which means it's physically larger than all the other SSDs we tested, and therefore can't be installed in low-profile systems. The front surface of the RevoDrive 350 board is covered with a decorative metal casing, which also acts as a heatsink for the base RAID controller chip. The SF-2282 controllers are located on the reverse side of the board and are devoid of any cooling.

To form the flash memory array, OCZ used chips from its parent company, Toshiba. The chips used are manufactured using a 19-nm process technology and have a capacity of 64 Gbps. The total amount of flash memory in the RevoDrive 350 480 GB is 512 GB, but 13% is reserved for internal needs - wear leveling and garbage collection.

It is worth noting that the architecture of the RevoDrive 350 is not unique. There are several more models of similar SSDs on the market that work on the principle of a “RAID array of SATA SSDs based on SandForce controllers”. However, all such solutions, like the OCZ PCIe drive under consideration, have an unpleasant drawback - their write performance degrades over time. This is due to the peculiarities of the internal algorithms of SandForce controllers, the TRIM operation for which does not return the write speed to the original level.

The indisputable fact that the RevoDrive 350 is one step below the next generation PCI Express drives is also emphasized by the fact that this drive is given only a three-year warranty, and its guaranteed write resource is only 54 TB - many times less than its competitors. Moreover, despite the fact that RevoDrive 350 is based on the same design as the server Z-Drive 4500, it does not have any protection against power surges. However, all this does not prevent OCZ, with its inherent audacity, to position the RevoDrive 350 as a premium solution at the level of the Intel SSD 750.

Plextor M6e Black Edition 256 GB

It should be noted right away that the Plextor M6e Black Edition drive is a direct successor of the well-known M6e model. The similarity of the novelty to its predecessor can be traced in almost everything, if we talk about the technical, not the aesthetic component. The new SSD also has a two-piece design, including the actual drive in M.2 2280 format and an adapter that allows you to install it in any regular PCIe x4 slot (or faster). It is also based on the eight-channel Marvell 88SS9183 controller, which communicates with the outside world via two PCI Express 2.0 lines. Just like in the previous version, the M6e Black Edition uses Toshiba's MLC flash memory.

And this means that despite the fact that the M6e Black Edition assembled looks like a half-height PCI Express x4 card, in fact, this SSD uses only two PCI Express 2.0 lanes. Hence the not-too-impressive speeds, which are only slightly faster than traditional SATA SSDs. Passport performance on sequential operations is limited to 770 MB / s, and on arbitrary - 105 thousand IOPS. It is worth noting that the Plextor M6e Black Edition works according to the legacy AHCI protocol, and this ensures its wide compatibility with various systems.

Despite the fact that the Plextor M6e Black Edition, like the Kingston HyperX Predator, is a combination of a PCI Express adapter and a "core" in the M.2 format of the board, it is impossible to determine this from the front side. The entire drive is hidden under a figured black aluminum casing, in the center of which a red heatsink is embedded, which should remove heat from the controller and memory chips. The designers' calculation is clear: a similar color scheme is widely used in various gaming hardware, so the Plextor M6e Black Edition will look harmoniously next to many gaming motherboards and video cards from most leading manufacturers.

The flash memory array in the Plextor M6e Black Edition is powered by Toshiba's second-generation 19nm MLC NAND chips with a capacity of 64Gbps. The reserve used for the replacement fund and the operation of internal wear-leveling and garbage collection algorithms is allocated 7 percent of the total. Everything else is available to the user.

Due to the use of a rather weak Marvell 88SS9183 controller with an external PCI Express 2.0 x2 bus, the Plextor M6e Black Edition drive should be considered a rather slow PCIe SSD. However, this does not prevent the manufacturer from referring this product to the upper price category. On the one hand, it is still faster than a SATA SSD, and on the other hand, it has good reliability characteristics: it has a long time between failures and is covered by a five-year warranty. However, no special technologies that can protect the M6e Black Edition from power surges or increase its resource are implemented in it.

Samsung SM951 256 GB

Samsung SM951 is the most elusive drive in today's testing. The fact is that initially this is a product for computer assemblers, so it is rather faded in retail sales. Nevertheless, if desired, it is still possible to buy it, so we did not refuse to consider the SM951. Moreover, judging by the characteristics, this is a very high-speed model. It is designed to work on the PCI Express 3.0 x4 bus, uses the AHCI protocol and promises impressive speeds: up to 2150 MB / s in sequential operations and up to 90,000 IOPS in random operations. But most importantly, despite all this, the Samsung SM951 is cheaper than many other PCIe SSDs, so looking for it on sale may have a very specific business case.

Another feature of the Samsung SM951 is that it comes in M.2 form. Initially, this solution is focused on mobile systems, so no adapters for full-size PCIe slots are included with the drive. However, this can hardly be considered a serious drawback - most flagship motherboards also have M.2 interface slots on board. In addition, the necessary adapter boards are widely available on the market. The Samsung SM951 itself is an M.2 2280 form factor board, the connector of which has an M type key, indicating the need for an SSD in four PCI Express lanes.

The Samsung SM951 is based on the exceptionally powerful Samsung UBX controller, developed by the manufacturer specifically for PCI Express SSDs. It is based on three cores with ARM architecture and in theory is able to work with both AHCI and NVMe commands. In the SSD in question, only AHCI mode is enabled in the controller. But an NVMe version of this controller will soon be seen in a new consumer SSD that Samsung is due to launch this fall.

Due to the OEM focus, no warranty period or predicted endurance is reported for the drive in question. These parameters must be declared by the assemblers of the systems in which the SM951 will be installed, or by the sellers. However, it should be noted that 3D V-NAND, which is now actively promoted by Samsung in consumer SSDs as a faster and more reliable type of flash memory, is not used in the SM951. Instead, it uses the usual planar Toggle Mode 2.0 MLC NAND, produced, presumably, using 16nm technology (some sources suggest a 19nm process technology). This means that the SM951 should not be expected to have the same high endurance as the flagship 850 PRO SATA drive. In this parameter, the SM951 is closer to the usual mid-range models, in addition, only 7 percent of the flash memory array is allocated for redundancy in this SSD. The Samsung SM951 does not have any special server-level technologies to protect data from power failures. In other words, the emphasis in this model is placed solely on the speed of work, and everything else is cut off to reduce the cost.

It is worth noting one more thing. Under high load, the Samsung SM951 exhibits quite serious heating, which in the end can even lead to the inclusion of throttling. Therefore, in high-performance systems for SM951, it is desirable to organize at least airflow, or better, close it with a radiator.

Comparative characteristics of tested SSDs

Compatibility Issues

Like any new technology, PCI Express SSDs are not yet 100% problem-free with any platform, especially older ones. Therefore, you have to choose the right SSD not only based on consumer characteristics, but also with an eye to compatibility. Here it is important to keep in mind two points.

First of all, different SSDs can use a different number of PCI Express lanes and different generations of this bus - 2.0 or 3.0. Therefore, before buying a PCIe drive, you need to make sure that the system where you plan to install it has a free slot with the required bandwidth. Of course, faster PCIe SSDs are backwards compatible with slower slots, but in this case, purchasing a high-speed SSD does not make much sense - it simply cannot reach its full potential.

The Plextor M6e Black Edition has the widest compatibility in this sense - it requires only two PCI Express 2.0 lanes, and such a free slot is sure to be found on almost any motherboard. Kingston HyperX Predator already needs four PCI Express 2.0 lanes: many motherboards also have such PCIe slots, but some cheap platforms may not have extra slots with four or more PCI Express lanes. This is especially true for motherboards built on low-level chipsets, the total number of lines in which can be cut down to six. Therefore, before purchasing a Kingston HyperX Predator, be sure to check that the system has a free slot with four or more PCI Express lanes.

The OCZ Revodrive 350 takes things a step further - it already requires eight PCI Express lanes. Such slots are usually implemented not by the chipset, but by the processor. Therefore, the best place to use such a drive is LGA 2011/2011-3 platforms, where the PCI Express processor controller has an excessive number of lanes, which allows servicing more than one video card. In systems with LGA 1155/1150/1151 processors, OCZ Revodrive 350 will be appropriate only if the graphics integrated into the CPU are used. Otherwise, in favor of a solid state drive, you will have to take away half the lines from the GPU by switching it to PCI Express x8 mode.

The Intel SSD 750 and Samsung SM951 are somewhat similar to the OCZ Revodrive 350: they are also preferable to use in CPU-powered PCI Express slots. However, the reason here is not the number of lanes - they require only four PCI Express lanes, but the generation of this interface: both of these drives are able to use the increased bandwidth of PCI Express 3.0. However, there is an exception: the latest Intel chipsets of the 100th series, designed for Skylake processors, received support for PCI Express 3.0, so in the latest LGA 1151 boards they can be installed without a twinge of conscience in chipset PCIe slots, which are connected to at least four lines.

The compatibility problem has a second part. To all the limitations associated with the bandwidth of various variations of PCI Express slots, there are also restrictions associated with the protocols used. The most trouble-free in this sense are SSDs that work through AHCI. Due to the fact that they emulate the behavior of a conventional SATA controller, they can work with any, even old, platforms: they are seen in the BIOS of any motherboards, they can be boot disks, and no additional drivers are required for their operation in the operating system. In other words, Kingston HyperX Predator and Plextor M6e Black Edition are two of the most hassle-free PCIe SSDs.

What about the other pair of AHCI drives? With them, the situation is a little more complicated. OCZ Revodrive 350 works in the operating system through its own driver, but even so, there are no problems with making this drive bootable. The situation is worse with Samsung SM951. Although this SSD communicates with the system using the legacy AHCI protocol, it does not have its own BIOS, and therefore it must be initialized by the BIOS of the motherboard. Unfortunately, support for this SSD is not available in all motherboards, especially older ones. Therefore, with full confidence we can only talk about its compatibility with boards based on the latest Intel chipsets of the ninetieth and hundredth series. In other cases, it may simply not be seen by the motherboard. Of course, this does not prevent using the Samsung SM951 in an operating system where it is easily initialized by the AHCI driver, but in this case, you will have to forget about the possibility of booting from a high-speed SSD.

But the biggest inconvenience can be caused by the Intel SSD 750, which works through the new NVMe interface. Drivers that are required to support SSDs using this protocol are present only in the latest operating systems. So, in Linux, NVMe support appeared in kernel version 3.1; The "native" NVMe driver is available in Microsoft systems starting with Windows 8.1 and Windows Server 2012 R2; and in OS X, compatibility with NVMe drives was added in version 10.10.3. In addition, NVMe SSD is not supported by all motherboards. In order for such drives to be used as bootable drives, the motherboard BIOS must also have the appropriate driver. However, manufacturers have built the necessary functionality only into the latest firmware versions released for the latest motherboard models. Therefore, support for booting the operating system from NVMe drives is available only on the most modern motherboards for enthusiasts based on the Intel Z97, Z170 and X99 chipsets. In older and cheaper platforms, users will only be able to use NVMe SSDs as second drives in a limited set of operating systems.

Despite the fact that we tried to describe all possible combinations of platforms and PCI Express drives, the main conclusion from what has been said is that the compatibility of PCIe SSDs with motherboards is far from being as obvious as in the case of SATA SSDs. Therefore, before purchasing any high-speed solid state drive that works through PCI Express, be sure to check its compatibility with a specific motherboard on the manufacturer's website.

Test configuration, tools and testing methodology

Testing is carried out in the Microsoft Windows 8.1 Professional x64 with Update operating system, which correctly recognizes and maintains modern solid state drives. This means that in the process of passing the tests, as in normal everyday use of the SSD, the TRIM command is supported and actively involved. Performance measurement is performed with drives in a "used" state, which is achieved by pre-filling them with data. Before each test, the drives are cleaned and maintained using the TRIM command. Between individual tests, a 15-minute pause is maintained, allotted for the correct development of garbage collection technology. All tests, unless otherwise noted, use randomized, incompressible data.

Applications and tests used:

Iometer 1.1.0

Measuring the speed of sequential reading and writing data in blocks of 256 KB (the most typical block size for sequential operations in desktop tasks). Estimates of speeds are performed within a minute, after which an average is calculated.
Measurement of random read and write speed in 4 KB blocks (this block size is used in the vast majority of real operations). The test is run twice - without a request queue and with a request queue with a depth of 4 commands (typical for desktop applications that actively work with a forked file system). The data blocks are aligned with the flash memory pages of the drives. Speeds are evaluated for three minutes, after which an average is calculated.
Establishing the dependence of random read and write speeds when the drive is working with 4-kilobyte blocks on the depth of the request queue (in the range from one to 32 commands). The data blocks are aligned with the flash memory pages of the drives. Speeds are evaluated for three minutes, after which an average is calculated.
Establishing the dependence of random read and write speeds when the drive is working with blocks of different sizes. Blocks from 512 bytes to 256 KB are used. The depth of the request queue during the test is 4 commands. The data blocks are aligned with the flash memory pages of the drives. Speeds are evaluated for three minutes, after which an average is calculated.
Measuring performance under a mixed multi-threaded load and establishing its dependence on the ratio between read and write operations. The test is carried out twice: for sequential reads and writes in 128 KB blocks, performed in two independent threads, and for random operations with 4 KB blocks, which are performed in four threads. In both cases, the ratio between reads and writes varies in 20 percent increments. Speeds are evaluated for three minutes, after which an average is calculated.
Investigation of SSD performance degradation when processing a continuous stream of random write operations. Blocks of 4 KB and a queue depth of 32 commands are used. The data blocks are aligned with the flash memory pages of the drives. The duration of the test is two hours, instantaneous speed measurements are taken every second. At the end of the test, the ability of the drive to restore its performance to its original values ​​is additionally checked due to the operation of the garbage collection technology and after the TRIM command has been processed.

CrystalDiskMark 5.0.2
Synthetic benchmark that returns typical SSD performance measured on a 1 GB disk area "on top" of the file system. From the entire set of parameters that can be evaluated using this utility, we pay attention to the speed of sequential read and write, as well as the performance of random reads and writes in 4-kilobyte blocks without a request queue and with a queue of 32 instructions deep.
PC Mark 8 2.0
A test based on emulating real disk load, which is typical for various popular applications. On the tested drive, a single partition is created in the NTFS file system for the entire available volume, and the Secondary Storage test is carried out in PCMark 8. As test results, both the final performance and the speed of execution of individual test traces generated by various applications are taken into account.
File Copy Tests
This test measures the speed of copying directories with files of various types, as well as the speed of archiving and unzipping files inside the drive. Used for copying standard remedy Windows - Robocopy utility, when archiving and unzipping - 7-zip archiver version 9.22 beta. Three sets of files are involved in the tests: ISO - a set that includes several disk images with software distributions; Program - a set that is a pre-installed software package; Work is a set of work files that includes office documents, photographs and illustrations, pdf files and multimedia content. Each of the sets has a total file size of 8 GB.

As a test platform, a computer with an ASUS Z97-Pro motherboard, a Core i5-4690K processor with an integrated Intel HD Graphics 4600 graphics core and 16 GB DDR3-2133 SDRAM is used. Drives with a SATA interface are connected to the SATA 6 Gb / s controller built into the motherboard chipset and operate in AHCI mode. PCI Express drives are installed in the first full-speed PCI Express 3.0 x16 slot. The drivers used are Intel Rapid Storage Technology (RST) 13.5.2.1000 and Intel Windows NVMe driver 1.2.0.1002.

The volume and speed of data transfer in benchmarks are indicated in binary units (1 KB = 1024 bytes).

In addition to the five main characters of this test - client SSDs with PCI Express interface, we added the fastest SATA SSD to the company - Samsung 850 PRO.

As a result, the list of tested models took the following form:

Intel SSD 750 400 GB (SSDPEDMW400G4, firmware 8EV10135);
Kingston HyperX Predator PCIe 480GB (SHPM2280P2H/480G, Firmware OC34L5TA);
OCZ RevoDrive 350 480 GB (RVD350-FHPX28-480G, firmware 2.50);
Plextor M6e Black Edition 256 GB (PX-256M6e-BK, firmware 1.05);
Samsung 850 Pro 256 GB (MZ-7KE256, firmware EXM01B6Q);
Samsung SM951 256 GB (MZHPV256HDGL-00000, firmware BXW2500Q).

Performance

Sequential read and write operations

The new generation of solid-state drives, transferred to the PCI Express bus, should first of all stand out for high sequential read and write speeds. And that's exactly what we see on the graph. All PCIe SSDs outperform the best SATA SSD, the Samsung 850 PRO. However, even such a simple load as sequential read and write shows huge differences between SSDs. various manufacturers. Moreover, the variant of the used PCI Express bus is not of decisive importance. The best performance here can be given by the Samsung SM951 PCI Express 3.0 x4 drive, and in second place is the Kingston HyperX Predator, which works via PCI Express 2.0 x4. The progressive NVMe drive Intel SSD 750 was only in third place.

Random reads

If we talk about random reading, as you can see from the diagrams, PCIe SSDs are not particularly different in speed from traditional SATA SSDs. Moreover, this applies not only to AHCI drives, but also to the product that works with the NVMe channel. In fact, only three participants in this test can demonstrate better performance than the Samsung 850 PRO in random read operations on small request queues: Samsung SM951, Intel SSD 750 and Kingston HyperX Predator.

Despite the fact that operations with a deep request queue for personal computers are not typical, we will still see how the performance of the SSD in question depends on the depth of the request queue when reading 4-kilobyte blocks.

The graph clearly shows how solutions that work through PCI Express 3.0 x4 can outperform all other SSDs. The curves corresponding to the Samsung SM951 and Intel SSD 750 are significantly higher than the curves of other drives. Another conclusion can be drawn from the above diagram: OCZ RevoDrive 350 is a shamefully slow solid state drive. On random read operations, it is about half behind the SATA SSD, which is due to its RAID architecture and the use of outdated second-generation SandForce controllers.

In addition to this, we suggest looking at how the speed of random reading depends on the size of the data block:

Here the picture is slightly different. As the block size grows, operations begin to look like sequential ones, so not only the architecture and power of the SSD controller, but also the bandwidth of the bus they use, begins to play a role. On larger block sizes, Samsung SM951, Intel SSD 750, and Kingston HyperX Predator provide the best performance.

Random Writes

Somewhere, the advantages of the NVMe interface, which provides low latencies, and the Intel SSD 750 controller with a high level of parallelism should have manifested themselves. In addition, the capacious DRAM buffer available in this SSD allows you to organize very efficient data caching. And as a result, the Intel SSD 750 delivers unsurpassed random write performance even when the request queue has a minimum depth.

To see more clearly what happens to random write performance as request queue depth increases, see the following graph, which shows 4K random write performance vs. request queue depth:

Intel SSD 750 performance scales up until the queue depth reaches 8 instructions. This is typical behavior for consumer SSDs. What sets Intel apart, however, is that its random write speeds are significantly faster than any other SSD, including the fastest PCIe models like the Samsung SM951 or the Kingston HyperX Predator. In other words, under random write load, the Intel SSD 750 offers fundamentally better performance than any other SSD. In other words, the transition to using the NVMe interface allows you to pump up the speed of random recording. And this is certainly an important characteristic, but first of all for server drives. Actually, the Intel SSD 750 is just a close relative of such models as the Intel DC P3500, P3600 and P3700.

The following graph shows random write performance versus data block size.

As block sizes increase, the Intel SSD 750 loses its undeniable advantage. The Samsung SM951 and Kingston HyperX Predator are starting to produce approximately the same performance.


As the cost of solid-state drives is no longer used as exclusively system drives and become ordinary work drives. In such situations, the SSD receives not only a refined load in the form of writes or reads, but also mixed requests, when read and write operations are initiated by different applications and must be processed simultaneously. However, full-duplex operation for modern SSD controllers remains a significant problem. When mixing reads and writes in the same queue, the speed of most consumer-grade SSDs sags noticeably. This was the reason for a separate study, in which we check how SSDs perform when it is necessary to process sequential operations interspersed. The next pair of charts show the most typical case for desktops, where the ratio of the number of reads and writes is 4 to 1.

Under sequential mixed loads with predominant read operations, which is typical for ordinary personal computers, the Samsung SM951 and Kingston HyperX Predator give the best performance. Random mixed load turns out to be more difficult for SSDs and leaves Samsung SM951 in the lead, but Intel SSD 750 moves to second place. At the same time, Plextor M6e Black Edition, Kingston HyperX Predator and OCZ RevoDrive 350 generally turn out to be noticeably worse than a regular SATA SSD.

The next couple of graphs give a more detailed picture of mixed load performance, showing the speed of an SSD versus the ratio of reads and writes to it.

All of the above is well confirmed in the above graphs. In a mixed workload with sequential operations, the Samsung SM951 shows the best performance, which feels like a fish in water in any work with serial data. For arbitrary mixed operations, the situation is slightly different. Both Samsung drives, both PCI Express 3.0 x4 SM951 and regular SATA 850 PRO, perform very well in this test, outperforming almost all other SSDs. In some cases, only the Intel SSD 750 can resist them, which, thanks to the NVMe command system, is perfectly optimized for working with random writes. And when mixed-trade workflow rises to 80 percent or more records, it jumps ahead.

Results in CrystalDiskMark

CrystalDiskMark is a popular and simple test application that runs "on top" of the file system, which allows you to get results that are easily replicated by ordinary users. The performance figures obtained in it should complement the detailed graphs that we built based on tests in IOMeter.

These four charts are only theoretical value, showing peak performance that is not achievable in typical client tasks. A request queue depth of 32 commands never occurs on personal computers, but in special tests it allows you to get maximum performance. And in this case, the leading performance by a wide margin is given by the Intel SSD 750, which has an architecture inherited from server drives, where a large depth of the request queue is quite in the order of things.

But these four diagrams are already of practical interest - they display the performance under load, which is typical for personal computers. And here the Samsung SM951 gives out the best performance, which lags behind the Intel SSD 750 only with random 4-kilobyte writes.

PCMark 8 2.0 Real Use Cases

The Futuremark PCMark 8 2.0 test package is interesting in that it is not synthetic in nature, but on the contrary, it is based on how real applications work. During its passage, real scenarios-traces of using a disk in common desktop tasks are reproduced, and the speed of their execution is measured. The current version of this test simulates a workload that is taken from actual Battlefield 3 and World of Warcraft game applications and software packages from Abobe and Microsoft: After Effects, Illustrator, InDesign, Photoshop, Excel, PowerPoint, and Word. The final result is calculated as the average speed that the drives show when passing the test tracks.

The PCMark 8 2.0 test, which evaluates the performance of storage systems in real applications, clearly tells us that there are only two PCIe drives that are fundamentally faster than conventional SATA models. These are Samsung SM951 and Intel SSD 750, which also win in many other tests. Other PCIe SSDs, such as Plextor M6e Black Edition and Kingston HyperX Predator, are more than one and a half times behind the leaders. Well, the OCZ ReveDrive 350 demonstrates frankly poor performance. It is more than twice as slow as the best PCIe SSDs and is inferior in speed even to the Samsung 850 PRO, which works via a SATA interface.

The integral result of PCMark 8 should be supplemented with performance indicators issued by flash drives when passing individual test tracks that simulate various real load scenarios. The fact is that under different loads, flash drives often behave a little differently.

Whatever application we are talking about, in any case, one of the SSDs with PCI Express 3.0 x4 interface gives the highest performance: either Samsung SM951 or Intel SSD 750. Interestingly, other PCIe SSDs in some cases generally only give speeds at the level of SATA SSDs . In fact, the advantage of the same Kingston HyperX Predator and Plextor M6e Black Edition over the Samsung 850 PRO can only be seen in Adobe Photoshop, Battlefield 3 and Microsoft Word.

Copying files

Keeping in mind that solid-state drives are being introduced into personal computers more and more, we decided to add to our methodology the performance measurement during normal file operations - when copying and working with archivers - that are performed "inside" the drive. This is typical disk activity that occurs when the SSD plays the role of not system drive, but a regular disk.

In the copy tests, the leaders are still the same Samsung SM951 and Intel SSD 750. However, if we are talking about large sequential files, then Kingston HyperX Predator can compete with them. I must say that with simple copying, almost all PCIe SSDs are faster than the Samsung 850 PRO. There is only one exception - Plextor M6e Black Edition. And the OCZ RevoDrive 350, which has consistently found itself in the position of a hopeless underdog in the rest of the tests, unexpectedly bypasses not only the SATA SSD, but also the slowest PCIe SSD.

The second group of tests was carried out during archiving and unzipping the directory with working files. The fundamental difference in this case is that half of the operations are performed with scattered files, and the other half with one large archive file.

The situation is similar when working with archives. The only difference is that here Samsung SM951 manages to confidently break away from all competitors.

How TRIM and background garbage collection work

When testing various SSDs, we always check how they process the TRIM command and whether they are able to collect garbage and restore their performance without support from the operating system, that is, in a situation where the TRIM command is not transmitted. Such testing was carried out this time as well. The scheme of this test is standard: after creating a long continuous load on data writing, which leads to degradation of the write speed, we disable TRIM support and wait 15 minutes, during which the SSD can try to recover on its own due to its own garbage collection algorithm, but without outside help operating system, and measure the speed. Then the TRIM command is forcibly sent to the drive - and after a short pause, the speed is measured again.

The results of such testing are shown in the following table, where for each tested model it is indicated whether it responds to TRIM by clearing an unused part of the flash memory and whether it can prepare clean flash memory pages for future operations if the TRIM command is not given to it. For drives that turned out to be able to carry out garbage collection without the TRIM command, we also indicated the amount of flash memory that was independently released by the SSD controller for future operations. For the case of operating the drive in an environment without TRIM support, this is just the amount of data that can be stored on the drive at a high initial speed after idle time.

Despite the fact that high-quality support for the TRIM command has become the industry standard, some manufacturers consider it acceptable to sell drives in which this command is not fully processed. Such a negative example is demonstrated by OCZ Revodrive 350. Formally, it understands TRIM, and even tries to do something when receiving this command, but there is no need to talk about a full return of the write speed to its original values. And there is nothing strange in this: the Revodrive 350 is based on SandForce controllers, which are notable for their irreversible performance degradation. Accordingly, it is also present in Revodrive 350.

All other PCIe SSDs work with TRIM just like their SATA counterparts. That is, ideally: in operating systems that issue this command to drives, performance remains at a consistently high level.

However, we want more - a high-quality drive should be able to carry out garbage collection without issuing a TRIM command. And here the Plextor M6e Black Edition stands out - a drive that is able to independently free up much more flash memory for upcoming operations than its competitors. Although, of course, offline garbage collection works to some extent on all the SSDs we tested, with the exception of the Samsung SM951. In other words, under normal use in today's environments, the performance of the Samsung SM951 will not degrade, but in cases where TRIM is not supported, this SSD is not recommended.

conclusions

We should probably start summing up by stating the fact that consumer SSDs with PCI Express interface are no longer exotic and not some kind of experimental products, but a whole market segment in which the fastest solid state drives for enthusiasts play. Naturally, this also means that there have been no problems with PCIe SSDs for a long time: they support all the functions that SATA SSDs have, but at the same time they are more productive and sometimes have some new interesting technologies.

At the same time, the client PCIe SSD market is not so crowded, and so far only companies with high engineering potential have been able to enter the cohort of manufacturers of such solid state drives. This is due to the fact that independent developers of mass-produced SSD controllers do not yet have designer solutions that allow them to start producing PCIe drives with minimal engineering effort. Therefore, each of the PCIe SSDs currently on store shelves is distinctive and unique in its own way.

In this test, we were able to bring together five of the most popular and most common PCIe SSDs targeted for use in personal computers. And according to the results of acquaintance with them, it becomes clear that buyers who want to switch to using solid-state drives with a progressive interface will not face any serious choice torment yet. In most cases, the choice will be unambiguous, the tested models differ so much in their consumer qualities.

In general, the most attractive PCIe SSD model turned out to be Samsung SM951. This is a brilliant PCI Express 3.0 x4 solution from one of the market leaders, which not only proved to be able to provide the highest performance in typical general workloads, but is also significantly cheaper than all other PCIe drives.

However, the Samsung SM951 is still not perfect. Firstly, it does not contain any special technologies aimed at improving reliability, but we would still like to have them in premium-level products. Secondly, this SSD is quite difficult to find on sale in Russia - it is not supplied to our country through official channels. Fortunately, we can offer to pay attention to a good alternative - Intel SSD 750. This SSD also runs via PCI Express 3.0 x4, and is only slightly behind the Samsung SM951. But it is a direct relative of server models, and therefore has high reliability and works on the NVMe protocol, which allows it to demonstrate unsurpassed speed on random write operations.

In principle, against the background of Samsung SM951 and Intel SSD 750, other PCIe SSDs look rather weak. However, there are still situations when they will have to prefer some other PCIe SSD model. The fact is that advanced Samsung and Intel drives are only compatible with modern motherboards built on Intel's ninetieth or hundredth series chipsets. In older systems, they can only work as a “second disk”, and loading the operating system from them will be impossible. Therefore, neither Samsung SM951 nor Intel SSD 750 are suitable for upgrading platforms of previous generations, and the choice will have to be made on the drive Kingston HyperX Predator, which, on the one hand, can provide good performance, and on the other hand, is guaranteed not to have any compatibility problems with older platforms.

In this article, we will explain the reasons for the success of the PCI bus and describe the high-performance technology that is coming to replace it - the PCI Express bus. We will also look at the history of development, the hardware and software levels of the PCI Express bus, the features of its implementation and list its advantages.

When in the early 1990s it appeared, then, in terms of its technical characteristics, it significantly exceeded all the tires that existed up to that moment, such as ISA, EISA, MCA and VL-bus. At that time, the PCI bus (Peripheral Component Interconnect - interaction of peripheral components), operating at a frequency of 33 MHz, was well suited for most peripheral devices. But today the situation has changed in many ways. First of all, the clock speeds of the processor and memory have increased significantly. For example, the clock frequency of processors has increased from 33 MHz to several GHz, while the operating frequency of PCI has increased to only 66 MHz. The emergence of technologies such as Gigabit Ethernet and IEEE 1394B threatened that the entire bandwidth of the PCI bus could go to serve a single device based on these technologies.

At the same time, the PCI architecture has a number of advantages over its predecessors, so it was not rational to completely revise it. First of all, it does not depend on the type of processor, it supports buffer isolation, bus mastering technology (bus capture) and PnP technology in full. Buffer isolation means that the PCI bus operates independently of the internal processor bus, which allows the processor bus to function independently of the speed and load of the system bus. Thanks to bus capture technology, peripheral devices can directly control the process of transferring data on the bus, instead of waiting for help from the central processor, which would affect system performance. Finally, Plug and Play support allows automatic configuration and configuration of devices using it and avoids fuss with jumpers and switches, which pretty much ruined the lives of owners of ISA devices.

Despite the undoubted success of PCI, at the present time it faces serious problems. Among them are limited bandwidth, lack of real-time data transmission functions and lack of support for next-generation network technologies.

Comparative characteristics of various PCI standards

It should be noted that the actual throughput may be less than the theoretical one due to the principle of the protocol and the features of the bus topology. In addition, the total bandwidth is distributed among all devices connected to it, therefore, the more devices sit on the bus, the less bandwidth goes to each of them.

Such standard improvements as PCI-X and AGP were designed to eliminate its main drawback - low clock speed. However, increasing the clock frequency in these implementations has resulted in a reduction in the effective length of the bus and the number of connectors.

The new generation of the bus, PCI Express (or PCI-E for short), was first introduced in 2004 and was designed to solve all the problems that its predecessor faced. Today, most new computers are equipped with a PCI Express bus. Although they also have standard PCI slots, the time is not far off when the bus will become history.

PCI Express Architecture

The bus architecture has a layered structure as shown in the figure.

The bus supports the PCI addressing model, which allows all currently existing drivers and applications to work with it. In addition, the PCI Express bus uses the standard PnP mechanism provided by the previous standard.

Consider the purpose of the various levels of organization PCI-E. At the software level of the bus, read / write requests are generated, which are transmitted at the transport level using a special packet protocol. The data layer is responsible for error-correcting coding and ensures data integrity. The basic hardware layer consists of a double simplex channel consisting of a transmit and receive pair, collectively referred to as a link. The total bus speed of 2.5 Gb/s means that the throughput for each PCI Express lane is 250 Mb/s each way. If we take into account the overhead costs of the protocol, then about 200 Mb / s is available for each device. This bandwidth is 2-4 times higher than what was available for PCI devices. And, unlike PCI, if the bandwidth is distributed among all devices, then it goes to each device in full.

To date, there are several versions of the PCI Express standard, which differ in their bandwidth.

PCI Express x16 bus bandwidth for different PCI-E versions, Gb/s:

• 32/64
• 64/128
• 128/256

PCI-E bus formats

At the moment, various options for PCI Express formats are available, depending on the purpose of the platform - a desktop computer, laptop or server. Servers that require more bandwidth have more PCI-E slots, and those slots have more trunks. In contrast, laptops may only have one line for medium-speed devices.

Video card with PCI Express x16 interface.

PCI Express expansion cards are very similar to PCI cards, but the PCI-E connectors are more grippy to ensure the card won't slip out of the slot due to vibration or during shipping. There are several form factors of PCI Express slots, the size of which depends on the number of lanes used. For example, a bus with 16 lanes is referred to as PCI Express x16. Although the total number of lanes can be as high as 32, in practice, most motherboards nowadays are equipped with a PCI Express x16 bus.

Smaller form factor cards can be plugged into larger form factor slots without compromising performance. For example, a PCI Express x1 card can be plugged into a PCI Express x16 slot. As in the case of the PCI bus, you can use a PCI Express extender to connect devices if necessary.

The appearance of connectors of various types on the motherboard. From top to bottom: PCI-X slot, PCI Express x8 slot, PCI slot, PCI Express x16 slot.

Express Card

The Express Card standard offers a very simple way to add hardware to a system. The target market for Express Card modules are laptops and small PCs. Unlike traditional desktop expansion cards, the Express card can be connected to the system at any time while the computer is running.

One of the popular varieties of Express Card is the PCI Express Mini Card, designed as a replacement for Mini PCI form factor cards. A card created in this format supports both PCI Express and USB 2.0. PCI Express Mini Card dimensions are 30×56 mm. PCI Express Mini Card can connect to PCI Express x1.

Benefits of PCI-E

PCI Express technology has gained advantages over PCI in the following five areas:

1. Better performance. With just one lane, the throughput of PCI Express is twice that of PCI. In this case, the bandwidth increases in proportion to the number of lines in the bus, the maximum number of which can reach 32. An additional advantage is that information can be transmitted on the bus in both directions simultaneously.
2. Simplification of input-output. PCI Express takes advantage of buses such as AGP and PCI-X while offering a less complex architecture and relatively simple implementation.
3. Layered architecture. PCI Express offers an architecture that can adapt to new technologies without the need for significant software upgrades.
4. New generation I/O technologies. PCI Express gives you new opportunities to receive data with the help of simultaneous data transfer technology, which ensures that information is received in a timely manner.
5. Ease of use. PCI-E greatly simplifies system upgrades and expansions by the user. Additional Express card formats, such as the ExpressCard, greatly increase the ability to add high-speed peripherals to servers and laptops.

Conclusion

PCI Express is a bus technology for connecting peripherals, replacing technologies such as ISA, AGP, and PCI. Its use significantly increases the performance of the computer, as well as the user's ability to expand and update the system.

I have been asked this question more than once, so now I will try to answer it as clearly and briefly as possible, for this I will give pictures of the PCI Express and PCI expansion slots on the motherboard for a better understanding and, of course, I will indicate the main differences in the characteristics, t .e. very soon, you will find out what these interfaces are and how they look.

So, to begin with, let's briefly answer this question, what is PCI Express and PCI in general.

What is PCI Express and PCI?

PCI is a computer parallel I/O bus for connecting peripherals to a computer motherboard. PCI is used to connect: video cards, sound cards, network cards, TV tuners and other devices. The PCI interface is outdated, so you probably won't be able to find, for example, a modern video card that connects via PCI.

PCI Express(PCIe or PCI-E) is a computer serial I/O bus for connecting peripherals to a computer motherboard. Those. this already uses a bidirectional serial connection, which can have several lines (x1, x2, x4, x8, x12, x16 and x32) the more such lines, the higher the throughput of the PCI-E bus. The PCI Express interface is used to connect devices such as video cards, sound cards, network cards, SSD drives and others.

There are several versions of the PCI-E interface: 1.0, 2.0 and 3.0 (version 4.0 will be released soon). This interface is usually designated, for example, like this PCI-E 3.0 x16, which stands for PCI Express 3.0 version with 16 lanes.

If we talk about whether, for example, a video card that has a PCI-E 3.0 interface on a motherboard that only supports PCI-E 2.0 or 1.0 will work, so the developers say that everything will work, but of course keep in mind that the bandwidth will be limited by the capabilities of the motherboard. Therefore, in this case, overpay for a video card with more new version PCI Express I think is not worth it ( if only for the future, i.e. You are planning to purchase a new motherboard with PCI-E 3.0). Also, vice versa, let's say your motherboard supports PCI Express 3.0 version, and the video card supports version 1.0, then this configuration should also work, but only with PCI-E 1.0 capabilities, i.e. there is no restriction here, since the video card in this case will work at the limit of its capabilities.

Differences between PCI Express and PCI

The main difference in characteristics is, of course, the bandwidth, for PCI Express it is much higher, for example, for PCI at 66 MHz, the bandwidth is 266 Mb / s, and for PCI-E 3.0 (x16) 32 Gb/s.

Externally, the interfaces are also different, so you won't be able to connect, for example, a PCI Express video card to a PCI expansion slot. PCI Express interfaces with a different number of lanes also differ, I will now show all this in the pictures.

PCI Express and PCI expansion slots on motherboards

PCI and AGP slots

PCI-E x1, PCI-E x16 and PCI slots

1. Hello! Please explain the difference in bandwidth between PCI Express 3.0 x16 and PCI Express 2.0 x16. There are still motherboards with PCI Express 2.0 x16 interface on sale. I'm with I will lose video performance if I install a new interface video cardPCI Express 3.0 to a computer with a motherboard, where there is only a connectorPCIe 2.0? I think that I will lose, because the totalbaud rate PCI Express 2.0 has - 16 GB / s, and the totalPCI Express 3.0 data transfer rate is twice as fast - 32 GB/s.
2. Hello! I have a computer with a powerful but not new Intel Core i7 2700K processor and a motherboard that has a PCI Express 2.0 slot. Tell me, if I buy a new PCI Express 3.0 interface video card, then this video card will work twice as slow as if I had a motherboard with a connector PCI Express 3.0? Does that mean I need to change my computer?
3. Please answer this question. My motherboard has two connectors: PCI Express 3.0 and PCI Express 2.0, but in the connector PCI Express 3.0 new graphics card PCI Express 3.0 does not climb, the southbridge radiator interferes. If I install a video cardPCI-E 3.0 per slot PCI-E 2.0, will my video card perform worse than if it was installed in a PCI Express 3.0 slot?
4. Hello, I want to buy a used motherboard from a friend for two thousand rubles. Three years ago, he bought it for 7,000 rubles, but I'm confused by the fact that it has a slot for an interface video card PCI-E 2.0, and I have a video cardPCI-E 3.0. Will my graphics card on this motherboard run at full capacity or not?

Bandwidth difference between PCI Express 3.0 x16 and PCI Express 2.0 x16 interface

Hello friends! To date, on sale you can find motherboards with a slot for installing PCI Express 2.0 x16 video cards, and PCI Express 3.0x16. The same can be said about graphics adapters, there are video cards with an interface PCI-E 3.0, as well as PCI-E 2.0. If you look at the official specifications of the PCI Express 3.0 x16 and PCI Express 2.0 x16 interfaces, you will find out that the total data transfer rate of PCI Express 2.0 is- 16 GB / s, and PCI Express 3.0 is twice as large -32 GB/s. I will not delve into the wilds of the specifics of these interfaces and just tell you that there is such a big difference indata transfer rate is visible only in theory, but in practice it is very small.If you read articles on this topic on the Internet, thenyou will come to the conclusion that modern PCI Express 3.0 video cards operate at the same speed in PCI Express 3.0 x16 and PCI Express 2.0 x16 slots, and difference in throughputbetween PCI-E 3.0 x16 and PCI-E 2.0 x16 is only 1-2% video card performance loss. That is, it doesn't matter in which slot you install the video card, in PCI-E 3.0 or PCI-E 2.0, everything will work the same way.

But unfortunately all these articles were written in 2013 and 2014 and at that time there were no games like Far Cry Primal, Battlefield 1 and other new products that appeared in 2016. Also released in 2016 family of NVIDIA 10-series GPUs, such as GeForce GTX 1050 and GeForce GTX 1050 Ti graphics cards, and even GTX 1060. My experiments with new games and new video cards showed that the advantage of the PCI-E 3.0 interface overPCI-E 2.0 is no longer 1-2%, but on average 6-7%. What is interesting if the video card is lower class than GeForce GTX 1050 , then the percentage is less (2-3%) , and if vice versa, then more - 9-13%.

So, in my experiment, I used a video card GeForce GTX 1050 PCI-E 3.0 interface and socketed motherboard PCI Express 3.0 x16 and PCI Express 2.0 x16.

H graphics settings in games are always maximum.

1. Game FAR CRY PRIMAL. Interface PCI-E 3.0 showed an advantage over PCI-E 2.0 as always higher by 4-5 frames, which is approximately 4 % %.
2. Battlefield 1 game. The gap between PCI-E 3.0 and PCI-E 2.0 was 8-10 frames , which is about 9% as a percentage.
3. Rise of the Tomb Raider. Advantage PCI-E 3.0 averages 9- 10 fps or 9%.
4. Witcher. The advantage of PCI-E 3.0 was 3%.
5. Grand Theft Auto V. The advantage of PCI-E 3.0 is 5 fps or 5%.

That is, there is still a difference in bandwidth between the PCI-E 3.0 x16 and PCI-E 2.0 x16 interfaces and is not in favor of PCI-E 2.0. Therefore, I would not buy a motherboard with one PCI-E 2.0 slot at the moment.

A friend of mine bought a used motherboard for three thousand rubles. Yes, once it was heaped up and cost about ten thousand rubles, it has a lot of connectors SATA III and USB 3.0, also 8 slots for RAM, it supports RAID technology, etc., but it is built on an outdated chipset and a PCI Express 2.0 video card slot on it! In my opinion, I'd rather buy it. Why?

It may well happen that in a year or two the latest video cards will work only in the connector PCI Express 3.0 x16 , and on your motherboard there will be a morally obsolete and no longer used by manufacturers connector PCI Express 2.0 x16 . You buy a new video card, and it refuses to work in the old slot. Personally, I have already encountered many times that the video card PCI-E 3.0 did not run on the mat. connector board PCI-E 2.0, and Even updating the BIOS of the motherboard did not help.I also dealt with video cardsPCI-E 2.0 x16, which refused to work on older motherboards with an interface PCI-E 1.0 x16, although everywhere they write about backward compatibility.Cases when a PCI Express 3.0 x16 video card did not start on motherboards withPCI Express 1.0 x16, even more.

Well, do not forget about the appearance of the interface this year PCI Express 4.0. In this case, PCI Express 3.0 will be obsolete.