Almost all modern motherboards are currently equipped with a PCI-E x16 expansion slot. This is not surprising: a discrete graphics accelerator is installed in it, without which the creation of a productive personal computer is generally impossible. It is about its prehistory of appearance, technical specifications and possible modes of operation that will be discussed in the future.
Prehistory of the appearance of the expansion slot
In the early 2000s, with the AGP expansion slot, which at that time was used for installation, a situation developed when the maximum performance level was reached and its capabilities were no longer enough. As a result, the PCI-SIG consortium was created, which began to develop the software and hardware components of the future slot for installing graphics accelerators. The fruit of his creativity was the first PCI Express 16x 1.0 specification in 2002.
To ensure compatibility of the two discrete graphics adapter ports that existed at that time, some companies developed special devices that allowed installing outdated graphics solutions in a new expansion slot. In the language of professionals, such a development had its own name - PCI-E x16 / AGP adapter. Its main purpose is to minimize the cost of upgrading a PC by using components from the previous configuration of the system unit. But this practice did not become widespread for the reason that entry-level video cards on the new interface had a cost almost equal to the price of an adapter.
In parallel with this, simpler modifications of this expansion slot for external controllers were created, which replaced the usual PCI ports at that time. Despite the external similarity, these devices were significantly different. If AGP and PCI could boast of parallel information transfer, then PCI Express was a serial interface. Its higher performance was ensured by a significantly increased data transfer rate in duplex mode (information in this case could be transmitted in two directions at once).
Transfer rate and encryption method
In the designation of the PCI-E x16 interface, the number indicates the number of used bands for data transfer. In this case, there are 16. Each of them, in turn, consists of 2 pairs of wires for transmitting information. As noted, the higher speed is provided by the fact that these pairs are operating in full duplex mode. That is, the transfer of information can go in two directions at once.
To protect against possible loss or distortion of the transmitted data, a special information protection system called 8V / 10V is used in this interface. This designation is deciphered as follows: for correct and correct transmission of 8 data bits, it is necessary to supplement them with 2 service bits to perform a correctness check. In this case, the system is forced to transmit 20 percent of the service information, which does not carry a payload for the computer user. But this is a payment for the reliable and stable operation of the graphic subsystem of a personal computer, and you certainly cannot do without it.
PCI-E versions
The PCI-E x16 slot looks the same on all motherboards. Only here the speed of information transfer in each case may differ significantly. As a result, the speed of the device is also different. And the modifications of this graphical interface are as follows:
- 1st modification PCI - Express x16 v. 1.0 had a theoretical bandwidth of 8 GB / s.
- 2nd generation PCI - Express x16 v. 2.0 already boasted a doubled bandwidth - 16 GB / s.
- A similar trend has continued for the third version of this interface. In this case, this figure was set at around 64 GB / s.
It is impossible to visually distinguish by the location of the contacts. Moreover, they are compatible with each other. For example, if a graphics adapter card is installed in the 3.0 slot, which corresponds at the physical level to specifications 2.0, then the entire processing system will automatically switch to the lowest speed mode (that is, 2.0) and will continue to function with a bandwidth of 64 Gb / s. ...
First generation PCI Express
As noted earlier, PCI Express was first introduced in 2002. Its release marked the emergence of personal computers with several graphics adapters, which, moreover, could boast even one accelerator installed with increased performance. AGP 8X standard allowed to get a bandwidth of 2.1 Gb / s, and the first revision of PCI Express - 8 Gb / s.
Of course, there is no need to talk about an eight-fold increase. 20 percent of the increase was used for the transmission of service information, which made it possible to find errors.
Second modification PCI-E
The first generation of this one was replaced in 2007 by PCI-E 2.0 x16. Video cards of the 2nd generation, as noted earlier, were physically and programmatically compatible with the first modification of this interface. Only in this case the performance of the graphics system was significantly reduced to the level of the PCI Express 1.0 16x interface version.
Theoretically, the information transfer limit in this case was 16 Gb / s. But 20 percent of the gain received was spent on service information. As a result, in the first case, the real transfer was: 8 Gb / s - (8 Gb / s x 20%: 100%) = 6.4 Gb / s. And for the second version of the graphical interface, this value was already like this: 16 Gb / s - (16 Gb / s x 20%: 100%) = 12.8 Gb / s. Dividing 12.8 Gb / s by 6.4 Gb / s, we get a real practical increase in performance by 2 times between the 1st and 2nd PCI Express executions.
Third generation
The last and most relevant update to this interface was released in 2010. The peak PCI-E x16 speed in this case increased to 64 Gb / s, and the maximum power of the graphics adapter without additional power supply in this case can be equal to 75 W.
Configuration options with multiple graphics accelerators in one PC. Their pros and cons
One of the most important innovations of this interface is the ability to have multiple graphics adapters in x16 at once. In this case, video cards are combined with each other and form, in essence, a single device. Their overall performance is summed up, and this allows you to significantly increase the speed of the PC from the standpoint of processing the displayed image. For solutions from NVidia, this mode is called SLI, and for graphics processors from AMD - CrossFire.
The future of this standard
The PCI-E x16 slot will certainly not change for the foreseeable future. This will allow more productive video cards to be used as part of outdated PCs and, due to this, to carry out a phased upgrade of the computer system. Now the specifications of the 4th version of this data transfer method are being worked out. For graphics adapters, in this case, a maximum of 128 Gb / s will be provided. This will allow you to display the image on the monitor screen as "4K" or more.
Outcomes
Be that as it may, and PCI-E x16 is currently the uncontested graphics slot and interface. It will be relevant for a long time to come. Its parameters allow you to create both entry-level computer systems and high-performance PCs with multiple accelerators. It is due to this flexibility that no significant changes are expected in this niche.
Introduction In the past, the mainstream consumer was primarily 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 the competition between manufacturers was unfolding in the areas of performance and price, the gap between the solutions of the upper and lower levels remained quite small. This was partly because SSD technology itself dramatically improves the user experience with a computer, and thus implementation issues are relegated to the background for many. For the same reason, consumer SSDs have been blended into an older infrastructure that was originally geared towards mechanical hard drives. This greatly facilitated their implementation, however, it enclosed SSDs in a fairly narrow framework, which in many respects restrains both the increase in bandwidth and the decrease in the latency of the disk subsystem.
But up to a certain point, this state of affairs suited everyone. SSD technology was new, and users migrating to solid state drives were happy with their purchase even though they were essentially getting products that were actually far from their limits and their performance was constrained by artificial barriers. However, by today, SSD, perhaps, can be considered already the most 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 purchasing it in the very near future. And in these conditions, manufacturers are simply forced to think about how to develop, finally, full-fledged competition: to destroy all barriers and move to the release of wider product lines, fundamentally differing in the proposed characteristics. Fortunately, all the necessary ground has been prepared for this, and, first of all, most SSD developers have the desire and ability to start releasing products that work not through the hereditary SATA interface, but through the much more efficient PCI Express bus.
Since the SATA bandwidth is limited to 6 Gb / s, the maximum speed of the flagship SATA SSD does not exceed the value of the order of 500 MB / s. However, modern flash drives are capable of much more: when you think about it, they have more to do with system memory than mechanical hard drives. As for the PCI Express bus, now it is actively used as a transport layer when connecting graphics cards and other additional controllers that need to exchange data at high speed, for example, Thunderbolt. One PCI Express Gen 2 lane delivers 500 MB / s throughput, and 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 of the third generation. These are excellent numbers that are quite suitable for modern solid state drives.
From the foregoing, it naturally follows that, in addition to SATA SSDs, high-speed drives using the PCI Express bus should gradually find distribution in 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 PCI Express bus options. We decided to put them together and compare with each other in terms of performance and other parameters.
Test participants
Intel SSD 750 400 GBIn the solid-state drive market, Intel is pursuing a rather unconventional strategy and is not paying 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 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, which is worth a few words separately.
In terms of specific improvements to NVMe, the reduction in overhead deserves a mention first. For example, transferring the most typical 4K 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 latency at least twice. 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 available 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 removed altogether, and this is very important for server environments where a huge number 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 the Intel DC P3500, P3600 and P3700 server-class SSDs, but the Intel SSD 750 uses a 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 not too scary cost.
The Intel SSD 750 is a half-height PCIe x4 card that can utilize four 3.0 lanes and deliver sequential transfer rates up to 2.4GB / s and random operations up to 440K IOPS. True, the most capacious 1.2 TB modification is distinguished by the highest performance, 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 there is an aluminum radiator, and on the back side there is a decorative metal plate, which does not actually touch the microcircuits. It should be noted that the use of a radiator here is a necessity. The main controller of Intel's SSD generates a lot of heat, and under high load, even a drive equipped with such cooling can heat up to temperatures of the order of 50-55 degrees. But thanks to the pre-installed cooling, there are no hints of throttling - the performance remains constant even during continuous and intensive use.
The Intel SSD 750 is based on the server-level Intel CH29AE41AB0 controller, which operates at 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 over the bus than the usual SSD models.
As far as the flash memory used, this part of the Intel SSD 750 is not making any innovations. It is based on the usual Intel MLC NAND of the same production, released on a 20-nm process technology and having 64 and 128 Gbit cores interspersed. It should be noted that most other SSD manufacturers have given up on such memory for a long time, having switched to chips made according to finer standards. And Intel itself began to transfer to 16-nm memory not only its consumer, but also server drives. 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 amount of flash memory in this SSD is 480 GiB, of which only about 78 percent is available to the user. The rest is devoted to the swap 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 crystals, which allows you to successfully recover data even if one of the chips completely fails. In addition, Intel's SSD provides complete data protection against 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
The Kingston HyperX Predator is a much more traditional solution than the Intel SSD 750. Firstly, it works through the AHCI protocol, not NVMe, and secondly, to connect to the system, this SSD requires the more common PCI Express 2.0 bus. All this makes the Kingston variant a little slower - peak 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.
Along with this, the drive has a not quite 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 the usual 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. It is currently the fastest commercially available Marvell SSD controller with PCI Express support. However, Marvell will soon have faster successors with NVMe and PCI Express 3.0 support, which the Altaplus chip lacks.
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 chips MLC NAND 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 gave rise to a paradox: despite the fact that, according to its formal positioning, the Kingston HyperX Predator PCIe SSD is a premium product, it has only a three-year warranty, and the declared MTBF is significantly less than that of the flagship SATA SSD 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 spare flash memory included in it is used for garbage collection and wear leveling, but is primarily spent on replacing failed memory cells.
It remains only 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. Nevertheless, 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 is one of the oldest PCI Express consumer SSDs out there. Back in the days when none of the other manufacturers even thought about the release of client PCIe SSDs, the OCZ lineup had RevoDrive 3 (X2) - the prototype of the modern Revodrive 350. However, the roots of the OCZ PCIe drive go back to the past make it a somewhat strange proposition. against the background of current competitors. While most high-performance PC storage manufacturers use modern controllers that natively support PCI Express, the Revodrive 350 has a very sophisticated and clearly sub-optimal architecture. It is based on two or four (depending on size) SandForce SF-2200 controllers, which are assembled into a zero-level RAID array.
If we talk about the 480 GB OCZ Revodrive 350 model that took part in this testing, then in fact it is based on four SATA SSDs with a capacity of 120 GB each, each of which is based on its own SF-2282 chip (analogue of the widespread SF-2281) ... Then these elements are combined into a single four-component RAID 0 array. However, for this purpose, not quite the usual RAID controller is used, but the 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 so, 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 implements not quite a classic RAID 0, but some kind of its semblance with interactive load balancing. Instead of splitting the data stream into fixed-size blocks and transferring them sequentially to different SF-2282 controllers, VCA 2.0 technology assumes 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 solid state drive to the user. You cannot enter its BIOS, and it is impossible to find out that a RAID array is hidden in the depths of this SSD without a detailed acquaintance with the hardware stuffing. What's more, unlike conventional RAID arrays, the RevoDrive 350 supports all typical SSD features: SMART monitoring, TRIM and Secure Erase operation.
RevoDrive 350 is available as PCI Express 2.0 x8 cards. 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 sequential operation speed is limited to 1800 MB / s, and the random operation performance does not exceed 140 thousand IOPS.
It is worth noting that 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 the testing, and therefore 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 heatsink for the basic chip of the RAID controller. SF-2282 controllers are located on the back side of the board and lack any cooling.
OCZ used chips from its parent company, Toshiba, to form the flash memory array. The chips are manufactured according to the 19-nm process technology and have a capacity of 64 Gbps. The total flash memory in the RevoDrive 350 480 GB is 512 GB, but 13% is reserved for internal needs such as wear leveling and garbage collection.
It's 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 "RAID-array from SATA SSD based on SandForce controllers". However, all such solutions, as well as the considered OCZ PCIe drive, 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 of which does not return the write speed to the initial level.
The indisputable fact that RevoDrive 350 is one step lower than PCI Express drives of the new generation 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 - several times less than that of competitors. Moreover, despite the fact that the 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 like the Intel SSD 750.
Plextor M6e Black Edition 256 GB
It should be noted right away that the Plextor M6e Black Edition is a direct successor to 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 features a two-piece design, including an M.2 2280 drive itself and an adapter that allows it to be installed in any regular PCIe x4 slot (or faster). It is also based on an eight-channel Marvell 88SS9183 controller that communicates with the outside world via two PCI Express 2.0 lines. Just like in the previous modification, the M6e Black Edition uses Toshiba's MLC flash memory.
This means that while the assembled M6e Black Edition looks like a half-height PCI Express x4 card, this SSD actually uses only two PCI Express 2.0 lanes. Hence the not-so-impressive speeds, which are only slightly faster than traditional SATA SSDs. The rated performance on sequential operations is limited to 770 MB / s, and on arbitrary - 105 thousand IOPS. It should be noted 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 format of an M.2 board, it is impossible to determine it from the front side. The entire drive is hidden under a curly black aluminum casing in the center of which a red heatsink is embedded, which is supposed to remove heat from the controller and memory chips. The calculation of the designers 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 array of flash memory in the Plextor M6e Black Edition is recruited with Toshiba's second generation 19-nm MLC NAND chips with a capacity of 64 Gbps. 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 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 hand, 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 resource are not implemented in it.
Samsung SM951 256 GB
The Samsung SM951 is the most elusive drive in our test today. The fact is that initially it was a product for computer assemblers, so it is presented rather faded in retail. 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 focused 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 searching for it on the market may have a very specific economic justification.
Another feature of the Samsung SM951 is that it comes in M.2 form. 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 have M.2 interface slots on board. In addition, the necessary adapter boards are widely available on the market. The Samsung SM951 itself is a M.2 2280 form-factor board, the connector of which has a type M key, indicating the need for an SSD in four PCI Express lanes.
The Samsung SM951 is based on the extremely 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 under consideration, 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 slated to launch this fall.
Due to the OEM focus, the drive in question has not been reported with a warranty period or predicted endurance. 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 Samsung is now actively promoting in consumer SSDs as a faster and more reliable form 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 you shouldn't expect the SM951 to have the same high endurance as the flagship SATA 850 PRO drive. By this parameter, the SM951 is closer to the usual mid-range models, moreover, only 7 percent of the flash memory array is allocated for redundancy in this SSD. Samsung SM951 lacks any special server-level technologies to protect data from power failures. In other words, the emphasis in this model is solely on the speed of work, and everything else is cut off to reduce cost.
There is one more point worth noting. Under high load, the Samsung SM951 demonstrates a fairly serious heating, which in the end can even lead to throttling. Therefore, in high-performance systems for the SM951, it is desirable to organize at least airflow, and it is better to close it with a radiator.
Comparative characteristics of tested SSD
Compatibility issues
As with any new technology, PCI Express SSDs cannot yet boast 100% problem-free performance 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 on compatibility. And 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 backward compatible with slower slots, but in this case, purchasing a high-speed SSD doesn't make much sense - it simply won't be able to unleash its full potential.
The Plextor M6e Black Edition has the broadest compatibility in this sense - it requires only two PCI Express 2.0 lanes, and such a free slot will certainly 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-end chipsets, the total number of lines in which can be cut down to six. Therefore, before purchasing Kingston HyperX Predator, be sure to check that your system has a free slot with four or more PCI Express lanes.
The OCZ Revodrive 350 sets the task more difficult - it already requires eight PCI Express lanes. Such slots are usually realized 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 excessive number of lines, which allows servicing 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 a solid-state drive, you will have to take away half of the lines from the GPU, putting it into PCI Express x8 mode.
Intel SSD 750 and Samsung SM951 are somewhat similar to OCZ Revodrive 350: they are also preferable to use in PCI Express slots powered by the processor. However, the reason is not in the number of lines - they only need four PCI Express lanes, but in the generation of this interface: both of these drives are able to use the increased PCI Express 3.0 bandwidth. However, there is an exception: the latest Intel hundredth series system logic kits, designed for Skylake processors, have received PCI Express 3.0 support, therefore, in the latest LGA 1151 motherboards, 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. To all the limitations associated with the bandwidth of various variations of PCI Express slots, there are also limitations associated with the protocols used. The most problem-free in this sense are SSDs that work through 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 seen in the BIOS of any motherboard, 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? The situation with them is a little more complicated. The OCZ Revodrive 350 runs in the operating system through its own driver, but even so, there are no problems making this drive bootable. The situation is worse with the Samsung SM951. Although this SSD communicates with the system through the legacy AHCI protocol, it lacks 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 full confidence about its compatibility with motherboards 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 does not prevent you from using the Samsung SM951 in the 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. The drivers required to support solid state drives using this protocol are only present in the latest operating systems. So, in Linux, NVMe support appeared in the 3.1 kernel; The "innate" NVMe driver is available in Microsoft systems starting with Windows 8.1 and Windows Server 2012 R2; and on OS X, NVMe compatibility was added in 10.10.3. In addition, not all motherboards support NVMe SSDs. In order for such drives to be used as boot drives, the motherboard BIOS must also have a corresponding driver. However, manufacturers have built the necessary functionality only into the latest firmware versions released for the most recent models of motherboards. Therefore, support for booting the operating system from NVMe drives is available only on the most modern enthusiast motherboards based on 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 this: the compatibility of PCIe SSD with motherboards is not as obvious as in the case of SATA SSDs. Therefore, before purchasing any high-speed SSD that works 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 operating system Microsoft Windows 8.1 Professional x64 with Update, which correctly recognizes and maintains modern solid-state drives. This means that the TRIM command is supported and actively used during the tests, as in normal day-to-day use of the SSD. Performance is measured with drives in a "used" state by pre-filling them with data. Drives are cleaned and serviced by the TRIM command before each test. There is a 15-minute pause between individual tests, which is allotted for the correct practice 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 read and write data in blocks of 256 KB (the most typical block size for sequential operations in desktop tasks). The estimation of the speeds is carried out within a minute, after which the average is calculated.
Measuring the speed of random read and write in 4 KB blocks (this block size is used in the overwhelming majority of real 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 actively working with a branched file system). Data blocks are aligned relative to the flash drive pages. The assessment of the speeds is carried out within three minutes, after which the average is calculated.
Determination of the dependence of the random read and write speeds during operation of a drive with 4K blocks on the depth of the request queue (in the range from one to 32 commands). Data blocks are aligned relative to the flash drive pages. The assessment of the speeds is carried out within three minutes, after which the average is calculated.
Determination of the dependence of the random read and write speeds when the drive is operating with blocks of different sizes. Blocks from 512 bytes to 256 KB in size are used. The depth of the request queue during the test is 4 commands. Data blocks are aligned relative to the flash drive pages. The assessment of the speeds is carried out within three minutes, after which the average is calculated.
Measurement of performance under a mixed multithreaded 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 read and write operations is varied in 20 percent increments. The assessment of the speeds is carried out within three minutes, after which the average is calculated.
Investigation of SSD performance degradation when processing a continuous random write workflow. The blocks are 4 KB and the queue depth is 32 commands. Data blocks are aligned relative to the flash drive pages. 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 work of the garbage collection technology and after the TRIM command has been executed.
CrystalDiskMark 5.0.2
A synthetic benchmark that provides typical performance metrics for solid-state drives as measured on a 1GB disk area “on top” of the file system. Of the entire set of parameters that can be estimated using this utility, we pay attention to the sequential read and write speed, as well as the performance of random reads and writes in 4K blocks without a request queue and with a queue of 32 commands deep.
PCMark 8 2.0
A benchmark based on the emulation of a real disk load, which is typical for various popular applications. On the tested drive, a single NTFS partition is created for the entire available space, and the Secondary Storage test is carried out in PCMark 8. As test results, both the final performance and the execution speed 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 different types, as well as the speed of archiving and unzipping files inside the drive. To copy, a standard Windows tool is used - the Robocopy utility, while archiving and unpacking - the 7-zip archiver version 9.22 beta is used. Three sets of files are involved in the tests: ISO - a set that includes several disk images with software distributions; Program - a set, which is a preinstalled 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.
The test platform is 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. SATA drives connect to the SATA 6Gb / s controller built into the motherboard chipset and operate in AHCI mode. PCI Express drives are installed in the first PCI Express 3.0 x16 full speed 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 PCI Express interface, we have added to them the fastest SATA SSD - Samsung 850 PRO.
As a result, the list of tested models looks like this:
Intel SSD 750 400 GB (SSDPEDMW400G4, firmware 8EV10135);
Kingston HyperX Predator PCIe 480 GB (SHPM2280P2H / 480G, OC34L5TA firmware);
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, be distinguished by high sequential read and write speeds. And this is what we see on the chart. All PCIe SSDs outperform the best SATA SSD, the Samsung 850 PRO. However, even a simple load like sequential read and write 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 obtained from the PCI Express 3.0 x4 drive Samsung SM951, and in second place is the Kingston HyperX Predator operating via PCI Express 2.0 x4. The progressive NVMe drive Intel SSD 750 was only in third place.
Random read operations
If we talk about random reading, then as you can see from the diagrams, PCIe SSDs do not differ much 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 are not typical for personal computers, we will still see how the performance of the SSD in question depends on the depth of the request queue when reading 4K blocks.
The graph clearly shows how solutions working 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 those of other drives. One more 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 the time 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 propose to see how the random read speed depends on the size of the data block:
Here the picture is a little different. As the block size grows, operations begin to resemble 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 blocks, Samsung SM951, Intel SSD 750 and Kingston HyperX Predator provide the best performance.
Random write operations
Somewhere the benefits of the NVMe interface for low latencies and the Intel SSD 750 controller with high concurrency should have surfaced. In addition, the spacious DRAM buffer available in this SSD allows for very efficient data caching. As a result, the Intel SSD 750 delivers unrivaled random write speed even when the request queue is at its lowest.
You can more clearly see what happens to the random write performance as the request queue depth increases, see the following graph showing the dependence of the random write speed in 4K blocks on the request queue depth:
Intel SSD 750 performance scaling occurs until the queue depth reaches 8 commands. This is typical behavior for consumer SSDs. However, Intel's novelty is different in that its random write speeds are significantly higher than that of any other solid-state drives, including the fastest PCIe-models like the Samsung SM951 or the Kingston HyperX Predator. In other words, the Intel SSD 750 offers fundamentally better performance than any other SSD under a random write load. In other words, the transition to using the NVMe interface allows you to pump the speed of random recording. And this is certainly an important characteristic, but primarily for server drives. Actually, Intel SSD 750 is just a close relative of such models as Intel DC P3500, P3600 and P3700.
The following graph shows the dependence of the performance of random records on the size of the data block.
As block sizes increase, the Intel SSD 750 loses its clear advantage. Samsung SM951 and Kingston HyperX Predator start to give about the same performance.
As the cost becomes cheaper, solid-state drives are no longer used as exclusively system drives and become ordinary scratch disks. In such situations, the SSD receives not only the 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 for modern SSD controllers remains a significant challenge. Mixing reads and writes in the same queue slows down the speed of most consumer-grade SSDs. This was the reason for a separate study, in which we test how SSDs perform when it is necessary to handle sequential operations that come in interleaving. The following pair of diagrams shows the most typical case for desktops, when the ratio of the number of reads and writes is 4 to 1.
Under a sequential mixed load with predominantly read operations, which is typical for conventional personal computers, the best performance is provided by the Samsung SM951 and Kingston HyperX Predator. Random mixed load turns out to be a more difficult test for SSDs and leaves the Samsung SM951 in the lead, but Intel SSD 750 comes in second. At the same time, the Plextor M6e Black Edition, Kingston HyperX Predator and OCZ RevoDrive 350 turn out to be noticeably worse than a regular SATA SSD.
The next couple of graphs give a more detailed picture of performance under a mixed load, showing the dependence of the speed of an SSD on the ratio of read and write operations to it.
All of the above is well confirmed in the given graphs. Under mixed load with sequential operations, the Samsung SM951 performs best, which feels like a fish in water for any sequential data operation. For arbitrary mixed operations, the situation is slightly different. Both drives from Samsung, both the PCI Express 3.0 x4 SM951 and the regular SATA 850 PRO, give very good results in this test, outperforming almost all other SSDs in performance. In some cases, only Intel SSD 750 can resist them, which, thanks to the NVMe command system, is perfectly optimized for working with random records. And when the mix of operations flow rises to 80 percent or more, it jumps ahead.
Results in CrystalDiskMark
CrystalDiskMark is a popular and simple benchmarking application that runs on top of the file system and delivers results that are easily repeatable by ordinary users. The performance metrics obtained in it should complement the detailed graphs we built on the basis of tests in IOMeter.
These four diagrams are of theoretical value only, showing peak performance not achievable in typical client applications. The depth of the request queue of 32 commands in personal computers never happens, but in special tests it allows you to get the 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 depth of the request queue is quite common.
But these four diagrams are already of practical interest - they show the 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 4K records.
PCMark 8 2.0 Real-World Use Cases
The Futuremark PCMark 8 2.0 test suite is interesting in that it is not synthetic in nature, but rather based on how real applications work. In the course of its passage, real scenarios of disk usage in common desktop tasks are reproduced, and the speed of their execution is measured. The current version of this test simulates a load taken from real gaming applications 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 shown by drives when passing test tracks.
The PCMark 8 2.0 benchmark, 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 the usual models with a SATA interface. These are Samsung SM951 and Intel SSD 750, which win many other tests as well. 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 half the speed of the best PCIe SSDs, and at the same time is inferior in speed even to the Samsung 850 PRO, which works through the SATA interface.
The integral result of PCMark 8 must be supplemented with the performance indicators given by flash drives when passing separate test tracks, which simulate various variants of real load. The point is that flash drives often behave slightly differently under different loads.
Whatever application we are talking about, in any case, the highest performance is given by one of the SSDs with the PCI Express 3.0 x4 interface: either the Samsung SM951 or the Intel SSD 750. Interestingly, the rest of the PCIe SSDs in some cases generally only deliver speed at the level of the SATA SSD. ... 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
Bearing in mind that solid-state drives are being introduced into personal computers more and more, we decided to add performance measurement to our methodology for normal file operations - when copying and working with archivers - that are performed "inside" the drive. This is a typical disk activity that occurs when an SSD is not acting as a system drive, but as a regular disk.
In copying tests, the leaders are all the same Samsung SM951 and Intel SSD 750. However, when it comes to large sequential files, the Kingston HyperX Predator can compete with them. I must say that with a simple copy, almost all PCIe SSDs turn out to be faster than the Samsung 850 PRO. The only exception is the Plextor M6e Black Edition. And the OCZ RevoDrive 350, which in other tests stably found itself in the position of a hopeless outsider, unexpectedly bypasses not only the SATA SSD, but also the slowest PCIe SSD.
The second group of tests was carried out when zipping and unzipping a directory with working files. The fundamental difference between 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.
TRIM and background garbage collection
When testing various solid state drives, we always check how they handle the TRIM command and whether they are able to collect garbage and recover 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 using 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 unused portion of flash memory and whether it can prepare blank pages of flash memory for future operations if the TRIM command is not sent 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 using the drive in an environment without TRIM support, this is exactly the amount of data that can be saved to the drive at a high initial speed after an idle time.
While quality support from the TRIM team has become the industry standard, some manufacturers find it permissible to sell drives that do not fully support the TRIM team. OCZ Revodrive 350 demonstrates such a negative example. 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 the original values. And there is nothing strange in this: at the heart of the Revodrive 350 are SandForce controllers, which are distinguished by their irreversible performance degradations. Accordingly, it is also present in the 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, autonomous garbage collection works to some extent on all SSDs we tested, with the exception of the Samsung SM951. In other words, the performance of the Samsung SM951 will not degrade under normal use in modern environments, but in cases where TRIM is not supported, this SSD is not recommended.
conclusions
Probably, one should start summing up with a statement of the fact that consumer SSDs with PCI Express interface are no longer exotic and not some 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 are in a SATA SSD, but at the same time are more productive and sometimes have some new interesting technologies.At the same time, the market for client PCIe SSDs 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 SSD controllers do not yet have design solutions that would allow starting the production of PCIe-drives with minimal engineering efforts. Therefore, each of the PCIe SSDs currently presented on store shelves is distinctive and unique in its own way.
In this testing, we were able to bring together five of the most popular and most widely used PCIe SSDs for use in personal computers. And based on the results of acquaintance with them, it becomes clear that buyers who want to switch to using solid-state drives with a progressive interface are not threatened with any serious agony of choice. In most cases, the choice will be unambiguous, the tested models differ so much in their consumer qualities.
Overall, the most attractive PCIe SSD model was Samsung SM951... This is a brilliant solution from one of the market leaders, working through the PCI Express 3.0 x4 bus, which not only proved to be able to provide the highest performance in typical common workloads, but also significantly cheaper than all other PCIe drives.
However, the Samsung SM951 is still not perfect. Firstly, it does not have any special technologies aimed at increasing reliability, but I would still like to have them in premium 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 suggest paying attention to a good alternative - Intel SSD 750... This SSD also runs through 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 the Samsung SM951 and Intel SSD 750, the rest of the PCIe SSDs look rather weak. However, there are still situations when they will have to prefer some other model of PCIe SSD. The fact is that the advanced Samsung and Intel drives are compatible only with modern motherboards based on Intel chipsets of the ninetieth or hundredth series. In older systems, they are only able to work as a "second disk", and it will be impossible to boot the operating system from them. Therefore, neither Samsung SM951 nor Intel SSD 750 are suitable for upgrading platforms of previous generations, and the choice will have to be stopped on the drive. Kingston hyperx predator, which, on the one hand, can provide good performance, and on the other hand, it is guaranteed not to have any compatibility problems with old platforms.
PCI - Express (PCIe,PCI -E)- serial, universal bus first published July 22, 2002 of the year.
Is an general, unifying a bus for all nodes of the motherboard, in which all devices connected to it are adjacent. Came to replace the obsolete tire PCI and its variations AGP, due to the increased requirements for the bus bandwidth and the impossibility for reasonable means to improve the speed indicators of the latter.
The bus acts as switch by simply sending the signal from one point to another without changing it. This allows, without obvious loss of speed, with minimal changes and errors transmit and receive a signal.
Bus data goes simplex(full duplex), that is, simultaneously in both directions at the same speed, and signal along the lines, flows continuously, even when the device is turned off (like DC or bit signal of zeros).
Synchronization constructed by a redundant method. That is, instead of 8 bit information transmitted 10 bit, two of which are service (20% ) and in a certain sequence serve beacons for synchronization clock generators or identifying errors... Therefore, the declared speed for one line in 2.5 Gbps, in fact, is approximately 2.0 Gbps real.
Nutrition each device on the bus, selected separately and regulated using technology ASPM (Active State Power Management). It allows, when the device is idle (without signaling) underestimate its clock generator and switch the bus to the mode reduced power consumption... If there is no signal for a few microseconds, the device considered inactive and is transferred to the mode expectations(time depends on the type of device).
Speed characteristics in two directions PCI - Express 1.0 :*
1 x PCI -E ~ 500 Mbps
4x PCI -E ~ 2 Gbps
8 x PCI -E ~ 4 Gbps
16x PCI -E ~ 8 Gbps
32x PCI-E ~ 16 GB
* Data transfer speed in one direction is 2 times lower than these indicators
January 15, 2007 PCI —SIG released an updated specification called PCI-Express 2.0
The main improvement was in 2 times increased speed data transmission ( 5.0 GHz, against 2.5GHz in the old version). Improvement has also undergone point-to-point data transfer protocol(point-to-point), revised software component and added system software monitoring behind the bus speed. At the same time, compatibility with protocol versions PCI -E 1.x
In the new version of the standard ( PCI -Express 3.0 ), the main innovation will be modified coding system and synchronization... Instead of 10 bit systems ( 8 bit information, 2 bits service) will apply 130 bit (128 bit information, 2 bits service). This will reduce losses in speed from 20% to ~ 1.5%... Will also be redesigned synchronization algorithm transmitter and receiver, improved PLL(phase-locked loop).Transmission speed increase presumably 2 times(in comparison with PCI -E 2.0), wherein compatibility will remain with previous versions PCI —Express.
The PCI Express standard is one of the foundations of modern computers. PCI Express slots have long occupied a solid place on any motherboard in a desktop computer, replacing other standards such as PCI. But even the PCI Express standard has its own varieties and different connection patterns. On new motherboards, starting around 2010, you can see on one motherboard a whole scattering of ports designated as PCIE or PCI-E, which can differ in the number of lines: one x1 or several x2, x4, x8, x12, x16 and x32.
So let's find out why there is such confusion among the seemingly simple PCI Express peripheral port. And what is the purpose of each PCI Express x2, x4, x8, x12, x16 and x32 standard?
What is PCI Express Bus?
In the distant 2000s, when the outdated PCI standard (extended - interconnection of peripheral components) to PCI Express took place, the latter had one huge advantage: instead of a serial bus, which was PCI, a point-to-point access bus was used. This meant that each individual PCI port and the cards installed in it could take full advantage of the maximum bandwidth without interfering with each other, as it did when connecting to PCI. In those days, the number of peripheral devices inserted into expansion cards was abundant. Network cards, audio cards, TV tuners, and so on - all required a fair amount of PC resources. But unlike the PCI standard, which used a common bus for data transfer with several devices connected in parallel, PCI Express, when viewed in general, is a packet network with a star topology.
PCI Express x16, PCI Express x1 and PCI on one card
In layman's terms, imagine your desktop PC as a small store with one, two sellers. The old PCI standard was like a grocery store: everyone waited in the same queue to be served, experiencing speed issues with a limited one salesperson at the counter. PCI-E is more like a hypermarket: each customer follows their own individual route for groceries, and several cashiers take the order at the checkout.
Obviously, a hypermarket is several times faster than a regular store in terms of service speed, due to the fact that the store cannot afford the bandwidth of more than one seller with one checkout.
Also with dedicated data lanes for each expansion card or built-in motherboard components.
Influence of the number of lines on throughput
Now, to expand on our store-to-hypermarket metaphor, imagine that each department of the hypermarket has its own cashiers, reserved only for them. This is where the idea of multiple data transmission lanes comes in.
PCI-E has gone through many changes since its inception. Currently, new motherboards usually use version 3 of the standard already, with the faster version 4 becoming more common, with version 5 expected in 2019. But different versions use the same physical connections, and these connections can be made in four basic sizes: x1, x4, x8 and x16. (x32 ports exist, but are extremely rare on motherboards for regular computers).
Different physical sizes of PCI-Express ports allow them to be clearly divided according to the number of simultaneous connections to the motherboard: the larger the port is physically, the more maximum connections it can transfer to the card or vice versa. These compounds are also called lines... One line can be thought of as a track consisting of two signal pairs: one for sending data and the other for receiving.
Different versions of the PCI-E standard allow for different speeds on each lane. But generally speaking, the more lanes there are on a single PCI-E port, the faster data can flow between the peripheral and the rest of the computer.
Returning to our metaphor: if we are talking about one seller in a store, then the strip x1 will be the only seller serving one customer. The store with 4 cashiers already has 4 lines x4... And so on, you can describe the cashiers by the number of lines, multiplying by 2.
Various PCI Express Cards
Device types using PCI Express x2, x4, x8, x12, x16, and x32
For the PCI Express 3.0 version, the total maximum data transfer rate is 8 GT / s. In reality, the speed for the PCI-E 3 version is slightly less than one gigabyte per second per lane.
Thus, a device using a PCI-E x1 port, such as a low-power sound card or Wi-Fi antenna, will be able to transmit data at a maximum speed of 1 Gbps.
A card that physically fits into a larger slot - x4 or x8 a USB 3.0 expansion card, for example, can transfer data four or eight times faster, respectively.
The transfer speed of PCI-E x16 ports is theoretically limited by the maximum bandwidth of about 15 Gb / s. This is more than enough in 2017 for all modern graphics cards developed by NVIDIA and AMD.
Most discrete graphics cards use a PCI-E x16 slot
PCI Express 4.0 allows you to use 16 GT / s, and PCI Express 5.0 will use 32 GT / s.
But there are currently no components that can use that many lanes with maximum bandwidth. Modern top-end graphics cards usually use the x16 PCI Express 3.0 standard. It makes no sense to use the same lanes for a network card that will use only one line on the x16 port, since the Ethernet port is only able to transfer data up to one gigabit per second (which is about one-eighth of the bandwidth of one PCI-E lane - remember: eight bits in one byte).
You can find PCI-E SSDs on the market that support the x4 port, but these seem to be soon supplanted by the booming new M.2 standard. for solid state drives that can also use the PCI-E bus. High-end NICs and enthusiast hardware such as RAID controllers use a mix of x4 and x8 formats.
PCI-E Port and Lane Sizes May Vary
This is one of the most confusing tasks for PCI-E: a port can be made in x16 form factor, but have insufficient bandwidth to pass data, for example, for example, just x4. This is because even though PCI-E can carry an unlimited number of individual connections, there is still a practical limit on the chipset's bandwidth. Cheaper motherboards with more budget chipsets may only have one x8 slot, even though that slot can physically house an x16 card.
In addition, motherboards aimed at gamers include up to four full PCI-E slots with x16 and the same number of lanes for maximum bandwidth.
Obviously this can cause problems. If the motherboard has two x16 slots, but one of them has only x4 strips, then connecting a new graphics card will reduce the performance of the first by as much as 75%. This is, of course, only a theoretical result. The architecture of the motherboards is such that you will not see a dramatic drop in performance.
Correct configuration of two video graphics cards should use exactly two x16 slots if you want maximum comfort from a tandem of two video cards. To find out how many lines on your motherboard a particular slot has, the manual at the office will help. manufacturer's website.
Sometimes manufacturers even mark the number of lines on the PCB of the motherboard next to the slot
Be aware that a shorter x1 or x4 card can physically fit into a longer x8 or x16 slot. The contact configuration of the electrical contacts makes this possible. Naturally, if the card is physically larger than the slot, then it will not work to insert it.
Therefore, remember, when buying expansion cards or upgrading current ones, you must always remember both the size of the PCI Express slot and the number of lanes required.
PCI Express is a bus that is used to connect a variety of components to a desktop PC. It is used to connect video cards, network cards, sound cards, WiFi modules and other similar devices. The development of this bus was started by Intel in 2002. The PCI Special Interest Group, a non-profit organization, is currently developing new versions of this bus.
At the moment, the PCI Express bus has completely replaced such outdated buses as AGP, PCI and PCI-X. The PCI Express bus is located at the bottom of the motherboard in a horizontal position.
What is the difference between PCI Express and PCI
PCI Express is a bus that has been designed around the PCI bus. The main differences between PCI Express and PCI lie at the physical level. While PCI uses a common bus, PCI Express uses a star topology. Each PCI Express device is connected to a common switch with a separate connection.
The PCI Express software model follows the PCI model in many ways. Therefore, most of the existing CI controllers can be easily modified to use the PCI Express bus.
In addition, the PCI Express bus supports such new features as:
- Hot plugging devices;
- Guaranteed speed of data exchange;
- Energy consumption management;
- Integrity control of transmitted information;
How the PCI Express bus works
The PCI Express bus uses a bi-directional 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 rate can be provided by the PCI Express bus. Depending on the number of lanes supported, the sizing on the motherboard will differ. There are slots with one (x1), four (x4) and sixteen (x16) lines.
Visual demonstration of PCI Express and PCI slot sizes
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 an x1 slot in an x16 slot on your motherboard.
PCI Express bandwidth depends on the number of lanes and the bus version.
| One / both directions in Gbps | |||||||
| Number of lines | |||||||
| x1 | x2 | x4 | x8 | x12 | x16 | x32 | |
| 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 |
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