IntroductionIn the past, the mass consumer was primarily interested in only 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 competition between manufacturers, although it developed in the areas of performance and price, the gap between top- and bottom-level solutions remained quite 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 issues of specific implementation fade into the background for many. For the same reason, consumer SSDs were fit into the old infrastructure, which was originally focused on mechanical hard drives. This greatly facilitated their implementation, but placed SSDs within a fairly narrow framework, which largely restrained both the growth of throughput and the reduction in latency of the disk subsystem.

But until a certain time, this state of affairs suited everyone. SSD technology was new, and users migrating to SSDs were happy with their purchases even though they were essentially getting products that didn't actually perform at their best, with performance being held back by artificial barriers. However, by today, SSDs can perhaps be considered truly 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 purchasing one in the very near future. And in these conditions, manufacturers are simply forced to think about how to finally develop full-fledged competition: to destroy all barriers and move on to producing wider product lines that are fundamentally different in the characteristics offered. Fortunately, all the necessary ground has been prepared for this, and, first of all, most SSD developers have the desire and opportunity to start producing products that work not through the legacy SATA interface, but through the much more productive PCI Express bus.

Since SATA bandwidth is limited to 6 Gb/s, the maximum speed of flagship SATA SSDs does not exceed about 500 MB/s. However, modern flash memory-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 graphic cards and other additional controllers that require high-speed data exchange, for example, Thunderbolt. A single Gen 2 PCI Express lane provides 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 of 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 that are quite suitable for modern solid-state drives.

From the above, it naturally follows that in addition to SATA SSDs, high-speed drives using the PCI Express bus should gradually become widespread on the market. And this is really 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 versions 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 solid-state drive market, Intel adheres to a rather unconventional strategy and does not pay too much attention to the development of SSDs for the consumer segment, concentrating on products for servers. However, this does not make her proposals 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 exactly how the Intel SSD 750 400 GB was born, which received not only impressive performance characteristics and a number of server-level technologies 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. For example, sending the most common 4K blocks in the new protocol requires issuing 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 servicing up to 65536 queues, and each of them can contain up to 65536 commands. In fact, any restrictions are eliminated altogether, and this is very important for server environments where the disk subsystem may be subject to a huge number of simultaneous I/O operations.

But despite working through the NVMe interface, the Intel SSD 750 is still not a server drive, 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 cheaper ordinary MLC NAND, and in addition the firmware is modified. The manufacturer believes that thanks to such changes, the resulting product will appeal to enthusiasts, since it combines high power, a fundamentally new NVMe interface and a not too scary price.

The Intel SSD 750 is a half-height PCIe x4 card that can use four 3.0 lanes and achieve sequential transfer rates of up to 2.4 GB/s and random operation speeds of up to 440 thousand IOPS. True, the most capacious 1.2 TB modification has the highest performance, but the 400 GB version we received for testing is a little slower.

The drive board is completely covered with armor. On the front side it is an aluminum radiator, and on the back 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 an Intel SSD generates a lot of heat, and under high load, even a drive equipped with such cooling can heat up to temperatures of about 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. When you consider 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 across the bus than conventional SSD models.

As for the flash memory used, the Intel SSD 750 does not make any innovations in this area. It is based on regular Intel-made MLC NAND, produced using a 20-nm process technology and having cores with a volume of both 64 and 128 Gbit interspersed. It should be noted that most other SSD manufacturers abandoned such memory quite a long time ago, switching to chips made to thinner standards. And Intel itself has begun converting not only its consumer, but also server drives to 16nm memory. However, despite all this, the Intel SSD 750 is equipped with 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 amount of flash memory in 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 a RAID 5-like scheme, traditional for flagship drives, at the MLC NAND chip level, which allows you to successfully restore data even if one of the chips completely fails. In addition, the Intel SSD provides complete data protection against power failures. The Intel SSD 750 has two electrolytic capacitors, and their capacity is sufficient for normal 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 via 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 older platforms.

At the same time, the drive has a not entirely simple two-component design. The SSD itself is a board in the M.2 form factor, which is complemented by a PCI Express adapter that allows you to connect M.2 drives through regular full-size PCIe slots. The adapter is designed as 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, the 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, has eight channels for connecting flash memory. At the moment, this is the fastest commercially available SSD controller from Marvell with PCI Express support. However, Marvell will soon have faster successors with support for NVMe and PCI Express 3.0, which the Altaplus chip does not have.

Since Kingston itself does not produce either controllers or memory, assembling its SSDs from elements purchased from other manufacturers, it is not strange 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 from Kingston (and other companies), and primarily in consumer models.

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

Kingston HyperX Predator also does not provide any special data protection technologies. 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 backup 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 design of the HyperX Predator 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 at all prone to overheating - its maximum heat dissipation is only slightly higher than 8 W.

OCZ Revodrive 350 480 GB

The OCZ Revodrive 350 can rightfully be called one of the oldest consumer SSDs with a PCI Express interface. Back in the days when none of the other manufacturers even thought about releasing client PCIe SSDs, OCZ’s lineup included RevoDrive 3 (X2) - the prototype of the modern Revodrive 350. However, the roots of the OCZ PCIe drive make it a somewhat strange proposal. against the backdrop 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 implements 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 into a zero-level RAID array.

If we talk about the OCZ Revodrive 350 480 GB model that took part in this testing, then it is actually based on four SATA SSDs with a capacity of 120 GB, each of which is based on its own SF-2282 chip (analogue of the widely used SF-2281) . These elements are then combined into a single four-part RAID 0 array. However, for this purpose, not a very familiar RAID controller is used, but a proprietary virtualization processor (VCA 2.0) OCZ ICT-0262. However, it is very likely that this name hides a redesigned 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 if so, OCZ engineers wrote their own firmware and driver for this controller.

The uniqueness of the RevoDrive 350 software component lies in the fact that it implements not quite the classic RAID 0, but something similar to it with interactive load balancing. Instead of breaking the data stream into fixed-size blocks and sequentially transmitting them to different SF-2282 controllers, VCA 2.0 technology involves analysis and flexible redistribution of I/O operations depending on the current occupancy of flash memory controllers. Therefore, the RevoDrive 350 looks like a monolithic SSD to the user. It is impossible to enter its BIOS, and it is impossible to discover that a RAID array is hidden in the depths of this SSD without a detailed acquaintance with the hardware. Moreover, unlike conventional RAID arrays, RevoDrive 350 supports all typical SSD functions: SMART monitoring, TRIM and Secure Erase operation.

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

It is worth noting that the OCZ RevoDrive 350 is designed as a full-height PCI Express x8 board, that is, this drive is physically larger than all the other SSDs participating in testing, and therefore it cannot 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 radiator for the base RAID controller chip. The SF-2282 controllers are located on the reverse side of the board and do not have any cooling.

To form the flash memory array, OCZ used chips from its parent company, Toshiba. Chips produced using a 19-nm process technology and having a capacity of 64 Gbit are used. 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, operating 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 performance on write operations degrades over time. This is due to the peculiarities of the internal algorithms of SandForce controllers, the TRIM operation of which does not return the write speed to the original level.

The indisputable fact that the RevoDrive 350 is one step lower than the PCI Express drives of the new generation is emphasized by the fact that this drive has only a three-year warranty, and its guaranteed recording resource is only 54 TB - several times less than that of 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 characteristic audacity, from positioning the RevoDrive 350 as a premium solution at the Intel SSD 750 level.

Plextor M6e Black Edition 256 GB

It should be immediately noted that the Plextor M6e Black Edition drive is a direct successor to the well-known M6e model. The similarity of the new product to its predecessor can be seen in almost everything, if we talk about the technical rather than the aesthetic component. The new SSD also has a two-component design, including the drive itself in the M.2 2280 format and an adapter that allows you to install it in any regular PCIe x4 (or faster) slot. It is also based on an eight-channel Marvell 88SS9183 controller, which communicates with the outside world via two PCI Express 2.0 lines. Just like the previous modification, the M6e Black Edition uses Toshiba MLC flash memory.

This means that while the M6e Black Edition looks like a half-height PCI Express x4 card when assembled, this SSD actually only uses two PCI Express 2.0 lanes. Hence the not very impressive speeds, which are only slightly higher than the performance of traditional SATA SSDs. The nominal performance for sequential operations is limited to 770 MB/s, and for arbitrary operations – 105 thousand IOPS. It is worth noting that Plextor M6e Black Edition operates using 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 M.2 card format, 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 there is a red radiator 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 harmonious next to many gaming motherboards and video cards from most leading manufacturers.

The flash memory array in the Plextor M6e Black Edition is equipped with Toshiba's second-generation 19-nm MLC NAND chips with a capacity of 64 Gbit. The reserve used for the replacement fund and the operation of internal algorithms for leveling wear and garbage collection is allocated 7 percent of the total volume. 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 classifying this product in the upper price category. On the one hand, it is still faster than a SATA SSD, and on the other, it has good reliability characteristics: it has a long MTBF and is covered by a five-year warranty. However, no special technologies that can protect the M6e Black Edition from voltage surges or increase its service life are implemented in it.

Samsung SM951 256 GB

The 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 presented in retail sales rather poorly. However, if you wish, 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 fast-acting 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 for sequential operations and up to 90 thousand IOPS for random operations. But most importantly, with all this, the Samsung SM951 is cheaper than many other PCIe SSDs, so its search for sale may have a very specific economic justification.

Another feature of the Samsung SM951 is that it comes in M.2 format. Initially, this solution is aimed at 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 for sale. The Samsung SM951 itself is a board of the M.2 2280 form factor, the connector of which has an M type key, indicating the need for an SSD with four PCI Express lines.

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

Due to the OEM focus, neither the warranty period nor the predicted endurance are provided for the drive in question. Builders of systems into which the SM951 will be installed, or sellers must declare these parameters. 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 conventional planar Toggle Mode 2.0 MLC NAND, presumably produced 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 SATA 850 PRO drive. In this parameter, the SM951 is closer to conventional mid-level models; moreover, 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 solely on speed, and everything else is cut off to reduce cost.

One more point is worth noting. Under high load, the Samsung SM951 exhibits quite serious heating, which ultimately can even lead to throttling. Therefore, in high-performance systems, it is advisable to organize at least airflow for the SM951, or better yet, cover it with a radiator.

Comparative characteristics of tested SSDs

Compatibility issues

Like any new technology, solid-state drives with a PCI Express interface cannot yet boast of 100% trouble-free operation with any platform, especially older ones. Therefore, you have to choose a suitable SSD not only based on consumer characteristics, but also with an eye to compatibility. And here it is important to keep two points in mind.

First of all, different SSDs can use different numbers of PCI Express lanes and different generations of this bus - 2.0 or 3.0. Therefore, before purchasing 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 slow slots, but in this case, purchasing a high-speed SSD does not make too much sense - it simply will not be able to unleash 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 will probably be found on almost any motherboard. The Kingston HyperX Predator already requires four PCI Express 2.0 lanes: many boards 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 lower-level chipsets, the total number of lines of which can be reduced 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.

OCZ Revodrive 350 poses a more difficult problem - it already requires eight PCI Express lanes. Such slots are usually implemented not by the chipset, but by the processor. Therefore, the optimal place for using such a drive is LGA 2011/2011-3 platforms, where the PCI Express processor controller has an excess number of lanes, allowing it to service more than one video card. In systems with LGA 1155/1150/1151 processors, the OCZ Revodrive 350 will be appropriate only if the graphics built into the CPU are used. Otherwise, in favor of the solid-state drive, you will have to take away half the lines from the GPU, switching it to PCI Express x8 mode.

Intel SSD 750 and Samsung SM951 are somewhat similar to the OCZ Revodrive 350: they are also preferable to use in PCI Express slots powered by the processor. However, the reason here is not the number of lanes - they only require four PCI Express lanes, but the generation of this interface: both of these drives are capable of using the increased bandwidth of PCI Express 3.0. However, there is an exception: the latest Intel chipsets of the 100th series, designed for processors of the Skylake family, have 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, to which at least four lines.

There is a second part to the compatibility problem. In addition to all the restrictions associated with the throughput of various variations of PCI Express slots, there are also restrictions associated with the protocols used. The most problem-free in this sense are SSDs that operate via AHCI. Due to the fact that they emulate the behavior of a regular SATA controller, they can work with any, even old, platforms: they are visible in the BIOS of any motherboard, 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? The situation with them is a little more complicated. The OCZ Revodrive 350 runs in the operating system through its own driver, but even despite this, there are no problems with making this drive bootable. The situation is worse with Samsung SM951. Although this SSD communicates with the system via the legacy AHCI protocol, it does not have its own BIOS, and therefore must be initialized by the motherboard BIOS. Unfortunately, not all motherboards, especially old ones, support this SSD. Therefore, we can only speak with complete confidence about its compatibility with boards based on the latest Intel chipsets of the 90th and 100th series. In other cases, it may simply not be seen by the motherboard. Of course, this will not prevent you from 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 operates via the new NVMe interface. The drivers required to support SSDs that use this protocol are only available on the latest operating systems. Thus, in Linux, NVMe support appeared in kernel version 3.1; the “innate” 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 boot 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 loading the operating system from NVMe drives is available only on the most modern boards for enthusiasts, based on Intel Z97, Z170 and X99 chipsets. In older and cheaper platforms, users will be able to use NVMe SSDs only as second drives in a limited set of OSes.

Despite the fact that we tried to describe all possible combinations of platforms and PCI Express drives, the main conclusion from the above is this: the compatibility of PCIe SSDs with motherboards is not as obvious a question as in the case of SATA SSDs. Therefore, before purchasing any high-speed solid-state drive that operates via 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 services modern solid-state drives. This means that during the testing process, as in normal everyday use of the SSD, the TRIM command is supported and actively used. Performance measurements are 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. There is a 15-minute pause between individual tests, allotted for the correct development of garbage collection technology. All tests use randomized, incompressible data unless otherwise noted.

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). The speeds are estimated within a minute, after which the average is calculated.
Measuring the speed of random reading and writing in 4 KB blocks (this block size is used in the vast majority of real-life operations). The test is carried out 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 branched file system). Data blocks are aligned relative to the flash memory pages of the drives. The speed assessment is performed for three minutes, after which the average is calculated.
Establishing the dependence of random read and write speeds when operating a drive with 4 KB blocks on the depth of the request queue (ranging from one to 32 commands). Data blocks are aligned relative to the flash memory pages of the drives. The speed assessment is performed for three minutes, after which the average is calculated.
Establishing the dependence of random read and write speeds when the drive operates with blocks of different sizes. Blocks ranging in size from 512 bytes to 256 KB are used. The request queue depth during the test is 4 commands. Data blocks are aligned relative to the flash memory pages of the drives. The speed assessment is performed for three minutes, after which the average is calculated.
Measuring performance under mixed multi-threaded workloads and determining 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, executed in two independent threads, and for random operations with 4 KB blocks, executed in four threads. In both cases, the ratio between read and write operations varies in 20 percent increments. The speed assessment is performed for three minutes, after which the average is calculated.
Study of SSD performance degradation when processing a continuous stream of random write operations. Blocks of 4 KB in size and a queue depth of 32 commands are used. Data blocks are aligned relative to the flash memory pages of the drives. The test duration is two hours, instantaneous speed measurements are carried out 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 garbage collection technology and after running the TRIM command.

CrystalDiskMark 5.0.2
A synthetic test that provides typical performance indicators for solid-state drives, measured on a 1-gigabyte disk area “on top” of the file system. Of the entire set of parameters that can be assessed using this utility, we pay attention to the speed of sequential read and write, as well as the performance of random read and write of 4 KB blocks without a request queue and with a queue depth of 32 commands.
PCMark 8 2.0
A test based on emulating real disk load, which is typical for various popular applications. On the drive being tested, a single partition is created in the NTFS file system for the entire available volume, and the Secondary Storage test is run in PCMark 8. The test results take into account both the final performance and the execution speed of individual test traces generated by various applications.
File copy tests
This test measures the speed of copying directories with different types of files, as well as the speed of archiving and unzipping files inside the drive. For copying, a standard Windows tool is used - the Robocopy utility; for archiving and unzipping, the 7-zip archiver version 9.22 beta is used. The tests involve three sets of files: ISO – a set that includes several disk images with program distributions; Program – a set that is a pre-installed software package; Work – a set of work files, including office documents, photographs and illustrations, pdf files and multimedia content. Each set has a total file size of 8 GB.

The test platform is a computer with an ASUS Z97-Pro motherboard, a Core i5-4690K processor with integrated Intel HD Graphics 4600 and 16 GB DDR3-2133 SDRAM. Drives with a SATA interface connect to the SATA 6 Gb/s controller built into the motherboard chipset and operate in AHCI mode. Drives with a PCI Express interface 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 heroes of this test - client SSDs with a PCI Express interface, we also added the fastest SATA SSD - 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 480 GB (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 reads and writes

The new generation of solid-state drives, transferred to the PCI Express bus, should primarily be distinguished by high sequential read and write speeds. And this is exactly what we see on the graph. All PCIe SSDs turn out to be more productive than the best SATA SSD – Samsung 850 PRO. However, even something as simple as sequential reads and writes shows huge differences between SSDs from different manufacturers. Moreover, the version of the PCI Express bus used is not decisive. The best performance here can be achieved by the PCI Express 3.0 x4 drive of the Samsung SM951, and in second place is the Kingston HyperX Predator, working 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, then, as can be seen 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 for 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 are not typical for personal computers, we will still look at how the performance of the SSD in question depends on the depth of the request queue when reading 4 KB blocks.

The graph clearly shows how solutions running via 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 graphs of other drives. Based on the above diagram, one more conclusion can be drawn: the OCZ RevoDrive 350 is a shamefully slow solid-state drive. In random read operations, it is about half as good as a 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 random read speed depends on the size of the data block:

Here the picture is a little different. As the block size increases, operations begin to resemble sequential ones, so not only the architecture and power of the SSD controller begins to play a role, but also the bandwidth of the bus they use. On larger blocks, the best performance is provided by Samsung SM951, Intel SSD 750 and Kingston HyperX Predator.

Random writes

Somewhere, the benefits of the low-latency NVMe interface and the high-parallel Intel SSD 750 controller had to show up. In addition, the large DRAM buffer available in this SSD allows for very efficient data caching. As a result, the Intel SSD 750 delivers unmatched random write speeds even when the request queue is minimal.

You can more clearly see what happens to random write performance as the depth of the request queue increases in the following graph, which shows the dependence of the speed of random write in 4K blocks on the depth of the request queue:

The performance of the Intel SSD 750 scales until the queue depth reaches 8 commands. This is typical behavior for consumer SSDs. However, Intel's new product is different in that its random write speeds are significantly higher than any other solid-state drives, including the fastest PCIe models like the Samsung SM951 or Kingston HyperX Predator. In other words, under occasional write loads, the Intel SSD 750 offers fundamentally better performance than any other SSD. In other words, switching to the NVMe interface allows you to improve the random write speed. And this is certainly an important characteristic, but primarily for server drives. Actually, the Intel SSD 750 is precisely a close relative of such models as the Intel DC P3500, P3600 and P3700.

The following graph shows random write performance as a function of data block size.

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


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

With a sequential mixed load with predominant read operations, which is typical for conventional personal computers, the Samsung SM951 and Kingston HyperX Predator provide the best performance. A random mixed load turns out to be a more difficult test for SSDs and leaves the Samsung SM951 in the lead, but the Intel SSD 750 moves into second place. At the same time, the 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 pair of graphs gives a more detailed picture of performance under mixed loads, showing the dependence of SSD speed on the ratio of read and write operations on it.

Everything said above is well confirmed by the above graphs. With a mixed load with sequential operations, the best performance is shown by the Samsung SM951, which feels like a fish in water when working with any serial data. For arbitrary mixed operations the situation is slightly different. Both Samsung drives, the SM951 running via PCI Express 3.0 x4, and the regular SATA 850 PRO, give very good results 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 the share of records in the mixed transaction flow increases to 80 percent or higher, it leaps ahead.

Results in CrystalDiskMark

CrystalDiskMark is a popular and simple benchmark application that runs on top of the file system and produces results that are easily repeatable by ordinary users. The performance indicators obtained in it should complement the detailed graphs we built based on tests in IOMeter.

The four diagrams shown are of theoretical value only, showing peak performance that is not achievable in typical client workloads. There is never a request queue depth of 32 commands in personal computers, but in special tests it allows you to get maximum performance indicators. And in this case, the leading performance by a large margin is given by the Intel SSD 750, which has an architecture inherited from server drives, where a large request queue depth is quite normal.

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

PCMark 8 2.0, real use cases

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

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, the speed of which is fundamentally higher than that of conventional models with a SATA interface. These are Samsung SM951 and Intel SSD 750, which win in many other tests. Other PCIe SSDs, for example, Plextor M6e Black Edition and Kingston HyperX Predator, lag behind the leaders by more than one and a half times. Well, the OCZ ReveDrive 350 demonstrates frankly poor performance. It is more than twice as slow as the best PCIe SSDs and is even slower than the Samsung 850 PRO, which operates via a SATA interface.

The integral result of PCMark 8 must be supplemented with performance indicators produced by flash drives when passing individual test traces that simulate various real-life load options. The fact is that under different loads, flash drives often behave slightly differently.

Whatever the application we are talking about, in any case, the highest performance is provided by one of the SSDs with a PCI Express 3.0 x4 interface: either Samsung SM951 or Intel SSD 750. Interestingly, other PCIe SSDs in some cases generally only provide 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 widely, we decided to add to our methodology a measurement of performance during common file operations - when copying and working with archivers - which are performed “inside” the drive. This is a typical disk activity that occurs when the SSD acts not as a system drive, but as a regular disk.

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

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

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

How TRIM and Background Garbage Collection Work

When testing various SSDs, we always check how they handle 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 issued. Such testing was carried out this time as well. The design of this test is standard: after creating a long-term continuous load on writing data, which leads to write speed degradation, we disable TRIM support and wait 15 minutes, during which the SSD can try to recover on its own using its own garbage collection algorithm, but without outside help operating system, and measure the speed. Then the TRIM command is forced onto the drive - and after a short pause, the speed is measured again.

The results of this testing are shown in the following table, which shows for each model tested whether it responds to TRIM by clearing unused flash memory and whether it can procure clean flash memory pages for future operations if a TRIM command is not issued to it. For drives that were able to perform garbage collection without the TRIM command, we also indicated the amount of flash memory that was independently freed by the SSD controller for future operations. If the drive is used in an environment without TRIM support, this is exactly the amount of data that can be saved to the drive with a high initial speed after inactivity.

Despite the fact that high-quality support for the TRIM command has become an industry standard, some manufacturers consider it acceptable to sell drives that do not fully implement this command. Such a negative example is demonstrated by the OCZ Revodrive 350. Formally, it understands TRIM, and even tries to do something when receiving this command, but there is no talk of a complete return of the write speed to its original values. And there is nothing strange about this: the Revodrive 350 is based on SandForce controllers, which are distinguished by 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, ideal: 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 perform garbage collection without issuing the TRIM command. And here the Plextor M6e Black Edition stands out - a drive that can independently free up significantly more flash memory for upcoming operations than its competitors. Although, of course, to one degree or another, autonomous garbage collection works for all SSDs we tested, with the exception of the Samsung SM951. In other words, during normal use in modern 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 summarizing the results by stating the fact that consumer SSDs with the PCI Express interface are no longer exotic or some experimental products, but an entire market segment in which the fastest performing 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 design solutions that allow them to begin producing PCIe drives with minimal engineering effort. Therefore, each of the PCIe SSDs currently presented on store shelves is original and unique in its own way.

In this testing, we were able to bring together the five most popular and most common PCIe SSDs, aimed at operation as part of personal computers. And based on the results of getting to know them, it becomes clear that buyers who want to switch to using solid-state drives with a progressive interface will not face any serious pains of choice yet. In most cases, the choice will be clear, the tested models differ so much in their consumer qualities.

Overall, the most attractive PCIe SSD model turned out to be Samsung SM951. This is a brilliant solution from one of the market leaders, operating over the PCI Express 3.0 x4 bus, which not only turns out to be able to provide the highest performance in typical common 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 increasing reliability, but in premium-level products one would still like to have them. Secondly, this SSD is quite difficult to find for sale in Russia - it is not supplied to our country through official channels. Fortunately, we can suggest paying 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 using the NVMe protocol, which allows it to demonstrate unsurpassed speed in random write operations.

In principle, compared to the Samsung SM951 and Intel SSD 750, other SSDs with a PCIe interface 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 compatible only with modern motherboards built on Intel chipsets of the ninetieth or hundredth series. In older systems, they can only work as a “second disk”, and loading the operating system from them will be impossible. Therefore, neither the Samsung SM951 nor the Intel SSD 750 are suitable for upgrading platforms of previous generations, and the choice will have to be on the drive Kingston HyperX Predator, which, on the one hand, can provide good performance, and on the other, is guaranteed not to have any compatibility problems with older platforms.

WiFi modules and other similar devices. Intel began developing this bus in 2002. Now the non-profit organization PCI Special Interest Group is developing new versions of this bus.

At the moment, the PCI Express bus has completely replaced such obsolete buses as AGP, PCI and PCI-X. The PCI Express bus is located at the bottom of the motherboard in a horizontal position.

PCI Express is a bus that was developed based on the PCI bus. The main differences between PCI Express and PCI lie at the physical layer. While PCI uses a shared bus, PCI Express uses a star topology. Each device is connected to a common switch with a separate connection.

The PCI Express software model largely follows the PCI model. Therefore, most existing PCI controllers can be easily modified to use the PCI Express bus.

PCI Express and PCI slots on the motherboard

In addition, the PCI Express bus supports new features such as:

• Hot plugging of devices;
• Guaranteed data exchange speed;
• Energy management;
• Monitoring the integrity of transmitted information;

How does the PCI Express bus work?

The PCI Express bus uses a bidirectional serial connection to connect devices. Moreover, such a connection can have one (x1) or several (x2, x4, x8, x12, x16 and x32) separate lines. The more such lines are used, the higher the data transfer speed the PCI Express bus can provide. Depending on the number of lines supported, the grade size on the motherboard will be different. There are slots with one (x1), four (x4) and sixteen (x16) lines.

Visual demonstration of PCI Express slot dimensions

Moreover, any PCI Express device can work in any slot if the slot has the same or more lines. This allows you to install a PCI Express card with a x1 connector into a x16 slot on the motherboard.

PCI Express bandwidth depends on the number of lanes and bus version.

One way/both ways in Gbit/s
	Number of lines
PCIe 1.0	2/4	4/8	8/16	16/32	24/48	32/64	64/128
PCIe 2.0	4/8	8/16	16/32	32/64	48/96	64/128	128/256
PCIe 3.0	8/16	16/32	32/64	64/128	96/192	128/256	256/512
PCIe 4.0	16/32	32/64	64/128	128/256	192/384	256/512	512/1024

Examples of PCI Express devices

PCI Express is primarily used to connect discrete video cards. Since the advent of this bus, absolutely all video cards use it.

GIGABYTE GeForce GTX 770 graphics card

However, this is not all that the PCI Express bus can do. It is used by manufacturers of other components.

SUS Xonar DX sound card

SSD drive OCZ Z-Drive R4 Enterprise

#PCI

Attention! This article is about the PCI bus and its derivatives PCI64 and PCI-X! Do not confuse this with the newer tire (PCI Express), which is completely incompatible with the tires described in this FAQ.

PCI 2.0- the first version of the basic standard to become widespread, both cards and slots with a signal voltage of only 5V were used.

PCI 2.1- differed from 2.0 by the possibility of simultaneous operation of several bus-master devices (the so-called competitive mode), as well as the appearance of universal expansion cards capable of operating in both 5V and 3.3V slots. The ability to work with 3.3V cards and the presence of corresponding power lines in version 2.1 was optional. PCI66 and PCI64 extensions appeared.

PCI 2.2- a version of the basic bus standard that allows the connection of expansion cards with signal voltages of both 5V and 3.3V. 32-bit versions of these standards were the most common type of slots at the time of writing the FAQ. The slots used are 32-bit, 5V.
Expansion cards made in accordance with these standards have a universal connector and are able to work in almost all later types of PCI bus slots, and also, in some cases, in 2.1 slots.

PCI 2.3- the next version of the general PCI bus standard, expansion slots conforming to this standard are incompatible with PCI 5V cards, despite the continued use of 32-bit slots with a 5V key. Expansion cards have a universal connector, but are not able to work in 5V slots of earlier versions (up to 2.1 inclusive).
We remind you that the supply voltage (not signal!) 5V is maintained on absolutely all versions of PCI bus connectors.

PCI 64- an extension of the basic PCI standard, introduced in version 2.1, doubling the number of data lines, and therefore the throughput. The PCI64 slot is an extended version of the regular PCI slot. Formally, the compatibility of 32-bit cards with 64-bit slots (subject to the presence of a common supported signal voltage) is full, and the compatibility of a 64-bit card with 32-bit slots is limited (in any case there will be a loss of performance), exact data in each specific case can be found in the device specifications.
The first versions of PCI64 (derived from PCI 2.1) used a 64-bit 5V PCI slot and ran at a clock speed of 33 MHz.

PCI 66- the expansion of the PCI standard that appeared in version 2.1 with support for a clock frequency of 66 MHz, just like PCI64, allows you to double the bandwidth. Starting from version 2.2, it uses 3.3V slots (the 32-bit version is practically never found on PCs), the cards have a universal or 3.3V form factor. (There were also solutions based on version 2.1 that were casuistically rare on the 5V 66MHz PC market; such slots and boards were only compatible with each other)

PCI 64/66- a combination of the two technologies described above, allows for quadrupling the data transfer speed compared to the basic PCI standard, and uses 64-bit 3.3V slots, compatible only with universal and 3.3V 32-bit expansion cards. PCI64/66 standard cards have a universal (which has limited compatibility with 32-bit slots) or 3.3V form factor (the latter option is fundamentally incompatible with 32-bit 33MHz slots of popular standards)
Currently, the term PCI64 means PCI64/66, since 33MHz 5V 64-bit slots have not been used for quite a long time.

PCI-X 1.0- PCI64 expansion with the addition of two new operating frequencies, 100 and 133 MHz, as well as a separate transaction mechanism to improve performance when operating multiple devices simultaneously. Generally backward compatible with all 3.3V and generic PCI cards.
PCI-X cards are usually implemented in a 64-bit 3.3B format and have limited backward compatibility with PCI64/66 slots, and some PCI-X cards are in a universal format and are capable of working (although this has almost no practical value) in regular PCI 2.2 /2.3.
In difficult cases, in order to be completely confident in the functionality of the combination of motherboard and expansion card you have chosen, you need to look at the compatibility lists of the manufacturers of both devices.

PCI-X 2.0- further expansion of the capabilities of PCI-X 1.0, added speeds of 266 and 533 MHz, as well as parity error correction during data transfer (ECC). Allows splitting into 4 independent 16-bit buses, which is used exclusively in embedded and industrial systems, the signal voltage is reduced to 1.5V, but the connectors are backward compatible with all cards using a 3.3V signal voltage.

PCI-X 1066/PCI-X 2133- projected future versions of the PCI-X bus, with resulting operating frequencies of 1066 and 2133 MHz, respectively, initially intended for connecting 10 and 40 Gbit Ethernet adapters.

For all PCI-X bus options, there are the following restrictions on the number of devices connected to each bus:
66MHz - 4
100MHz - 2
133 MHz - 1 (2, if one or both devices are not on expansion boards, but are already integrated on one board along with the controller)
266.533 MHz and above -1.

That is why in some situations, in order to ensure stable operation of several installed devices, it is necessary to limit the maximum operating frequency of the used PCI-X bus (usually this is done with jumpers)

СompactPCI- a standard for connectors and expansion cards used in industrial and embedded computers. Mechanically not compatible with any of the "common" standards.

MiniPCI- a standard for boards and connectors for integration into laptops (usually used for wireless network adapters) and directly onto the surface. It is also mechanically incompatible with anything other than itself.

Types of PCI expansion cards:

Summary table of card and slot designs depending on the version of the standard:

Summary table of card and slot compatibility depending on version and design:

	Cards
Slots	PCI 2.0/2.1 5B	PCI 2.1 universal	PCI 2.2/2.3 universal	PCI64/5B (33MHz)	PCI64/universal	PCI64/3.3B	PCI-X/3.3B	PCI-X universal
PCI 2.0	Compatible	Compatible	Incompatible		Limited compatibility with performance loss	Incompatible
PCI 2.1	Compatible	Compatible	Limited compatibility	Limited compatibility with performance loss	Limited compatibility with performance loss	Incompatible
PCI 2.2	Compatible			Limited compatibility with performance loss	Limited compatibility with performance loss	Incompatible	Incompatible	Limited compatibility with performance loss
PCI 2.3	Incompatible	Limited compatibility	Compatible	Incompatible	Limited compatibility with performance loss	Incompatible	Incompatible	Limited compatibility with performance loss
PCIB 64/5B(33MHz)	Compatible	Compatible	Limited compatibility	Compatible	Limited compatibility with performance loss	Incompatible	Incompatible	Limited compatibility with performance loss
PCI64/3.3B	Incompatible	Limited compatibility	Compatible	Incompatible	Compatible	Compatible	Limited compatibility with performance loss	Limited compatibility with performance loss
PCI-X	Incompatible	Limited compatibility	Compatible	Incompatible	Compatible

When it comes to any interfaces in the context of computer systems, you need to be very careful not to “run into” incompatible interfaces for the same components within the system.

Fortunately, when it comes to the PCI-Express interface for connecting a video card, there will be practically no problems with incompatibility. In this article we will look at this in more detail, and also talk about what PCI-Express is.

Why is PCI-Express needed and what is it?

Let's start, as usual, with the very basics. PCI-Express (PCI-E) interface- this is a means of interaction, in this context, consisting of a bus controller and the corresponding slot (Fig. 2) on motherboard(to generalize).

This high-performance protocol is used, as noted above, to connect a video card to the system. Accordingly, the motherboard has a corresponding PCI-Express slot, where the video adapter is installed. Previously, video cards were connected via the AGP interface, but when this interface, simply put, “was no longer enough,” PCI-E came to the rescue, the detailed characteristics of which we will now talk about.

Fig.2 (PCI-Express 3.0 slots on the motherboard)

Key Characteristics of PCI-Express (1.0, 2.0 and 3.0)

Despite the fact that the names PCI and PCI-Express are very similar, their connection (interaction) principles are radically different. In the case of PCI-Express, a line is used - a bidirectional serial connection, of the point-to-point type; there can be several of these lines. In the case of video cards and motherboards (we do not take into account Cross Fire and SLI) that support PCI-Express x16 (that is, the majority), you can easily guess that there are 16 such lines (Fig. 3), quite often on motherboards with PCI- E 1.0, it was possible to see a second x8 slot for operation in SLI or Cross Fire mode.

Well, in PCI, the device is connected to a common 32-bit parallel bus.

Rice. 3. Example of slots with different numbers of lines

(as mentioned earlier, x16 is most often used)

The interface bandwidth is 2.5 Gbit/s. We need this data to track changes in this parameter in different versions of PCI-E.

Further, version 1.0 evolved into PCI-E 2.0. As a result of this transformation, we received twice the throughput, that is, 5 Gbit/s, but I would like to note that the graphics adapters did not gain much in performance, since this is just a version of the interface. Most of the performance depends on the video card itself; the interface version can only slightly improve or slow down data transfer (in this case there is no “braking”, and there is a good margin).

In the same way, in 2010, with a reserve, the interface was developed PCI-E 3.0, at the moment it is used in all new systems, but if you still have 1.0 or 2.0, then do not worry - below we will talk about the relative backward compatibility of different versions.

With PCI-E 3.0, the bandwidth has been doubled compared to version 2.0. There were also a lot of technical changes made there.

Expected to be born by 2015 PCI-E 4.0, which is absolutely not surprising for the dynamic IT industry.

Well, okay, let's finish with these versions and bandwidth figures, and let's touch on the very important issue of backward compatibility of different versions of PCI-Express.

Backwards compatible with PCI-Express 1.0, 2.0 and 3.0 versions

This question worries many, especially when choosing a video card for the current system. Since being content with a system with a motherboard that supports PCI-Express 1.0, doubts arise whether a video card with PCI-Express 2.0 or 3.0 will work correctly? Yes, it will be, at least that’s what the developers who ensured this compatibility promise. The only thing is that the video card will not be able to fully reveal itself in all its glory, but the performance losses, in most cases, will be insignificant.

On the contrary, you can safely install video cards with a PCI-E 1.0 interface in motherboards that support PCI-E 3.0 or 2.0; there are no restrictions at all, so rest assured about compatibility. If, of course, everything is in order with other factors, these include an insufficiently powerful power supply, etc.

Overall, we've talked quite a bit about PCI-Express, which should help you clear up a lot of confusion and doubt about compatibility and understanding the differences between PCI-E versions.

Support for PCI Express 3.0 interface in motherboards - a real advantage or a marketing ploy?

Over the past months, motherboards that declare support for the PCI Express 3.0 interface have begun to appear in the lineup of different manufacturers. The first to announce such solutions were ASRock, MSI and GIGABYTE. However, at the moment, there are absolutely no chipsets, graphics or central processors on the market that would support the PCI Express 3.0 interface.

Let us remember that the PCI Express 3.0 standard was approved last year. It has numerous advantages over its predecessors, so it is not surprising that manufacturers of video cards and motherboards want to implement it in their solutions as soon as possible. However, existing chipsets from Intel and AMD today are limited to supporting the PCI Express 2.0 standard. The only hope of taking advantage of the PCI Express 3.0 interface in the near future lies with the new Intel Ivy Bridge processors, which are scheduled to be announced only in March-April next year. These processors integrate a PCI Express 3.0 bus controller, but only graphics chips will be able to use it, since other components use the chipset controller.

Note that the matter is not limited to just replacing the processor. It is necessary to additionally update the BIOS settings and chipset firmware. In addition, on motherboards with several PCI Express x16 slots, a problem appears with “switches” - small chips that are located near each slot and are responsible for quickly reconfiguring the number of dedicated lines. These “switches” must also be compatible with the PCI Express 3.0 interface. It should be noted that nForce 200 or Lucid bridge chips only support the PCI Express 2.0 standard and they cannot work with the PCI Express 3.0 specification.

The last argument is that at the moment motherboard manufacturers do not have engineering samples of new processors from the Intel Ivy Bridge line or new graphics chips that support the PCI Express 3.0 specification at the hardware level. Therefore, the announced compatibility with this high-speed interface is theoretical and cannot, at the moment, be practically confirmed.

Thus, support for the PCI Express 3.0 specification by modern motherboards is purely a marketing ploy, the benefits of which the user can only receive in a few months by replacing the processor and updating software components.