PCI e x16 connector. All about the PCI and PCI Express bus - specifications, differences and compatibility

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

So, first, let's briefly answer the question, what exactly is PCI Express and PCI?

What is PCI Express and PCI?

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 The PCI interface is outdated, so you probably won’t be able to find, for example, a modern video card that connects via PCI.

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

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

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

Differences between PCI Express and PCI

The main difference in characteristics is, of course, throughput; for PCI Express it is much higher, for example, PCI at 66 MHz has a throughput of 266 MB/sec, and PCI-E 3.0 (x16) 32 Gb/s.

Externally, the interfaces are also different, so connecting, for example, a PCI Express video card to a PCI expansion slot will not work. PCI Express interfaces with different numbers of lanes are also different, I will now show all this in pictures.

PCI Express and PCI expansion slots on motherboards

PCI and AGP slots

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

PCI Express interfaces on video cards

That's all I have for now!

Introduction

Moore's Law states that the number of transistors on a silicon chip that is profitable to produce doubles every couple of years. But don't think that processor speeds also double every couple of years. This is a common misconception among many, and users often expect PC performance to scale exponentially.

However, as you probably noticed, the top processors on the market have been stuck at the level between 3 and 4 GHz for about six years now. And the computer industry had to look for new ways to increase computing performance. The most important of these methods is to maintain a balance between platform components that use the PCI Express bus, an open standard that allows high-speed video cards, expansion cards and other components to exchange information. And the PCI Express interface is no less important for scaling performance than multi-core processors. While dual-core, quad-core, and six-core processors can only be loaded with thread-optimized applications, every program installed on your computer interacts in some way with components connected via PCI Express.

Many journalists and experts expected that motherboards and chipsets supporting the next generation PCI Express 3.0 interface would appear in the first quarter of 2010. Unfortunately, backward compatibility problems delayed the release of PCI Express 3.0, and today it has already been six months, but we are still waiting official information regarding the publication of the new standard.

However, we talked to the PCI-SIG (Special Interest Group, which is responsible for the PCI and PCI Express standards), which allowed us to get some answers.

PCI Express 3.0: plans

Al Yanes, President and Chairman of PCI-SIG, and Ramin Neshati, Chairman of PCI-SIG Serial Communications Workgroup, shared current plans for the implementation of PCI Express 3.0.

On June 23, 2010, version 0.71 of the PCI Express 3.0 specification was released. Jans argued that version 0.71 should fix all the backwards compatibility issues that led to the initial delay. Neshati noted that the main compatibility issue was the "DC wandering" feature, which he explained was that PCI Express 2.0 and earlier devices "didn't provide the necessary 0s and 1s" to comply with the PCI Express 3.0 interface.

Today, with the backward compatibility issues resolved, PCI-SIG is ready to release the 0.9 baseline "later this summer." And after this basic version, version 1.0 is expected in the fourth quarter of this year.

Of course, the most intriguing question is when PCI Express 3.0 motherboards will hit store shelves. Neshati noted that he expects the first products to appear in the first quarter of 2011 (triangle "FYI" in the picture with the plan).

Neshati added that between versions 0.9 and 1.0 there should be no changes at the silicon level (that is, all changes will affect only software and firmware), so some products should reach the market before the final 1.0 specification. And products can already be certified to PCI-SIG's "Integrator's List" (triangle "IL"), which is a variant of the PCI-SIG compliance logo.

Neshati jokingly referred to the third quarter of 2011 as the "Fry's and Buy" date (probably referring to Frys.com, Buy.com or Best Buy). That is, during this period we should expect the appearance of a large number of products with PCI Express 3.0 support in retail stores and online stores.

PCI Express 3.0: Designed for Speed

For end users, the main difference between PCI Express 2.0 and PCI Express 3.0 will be the significant increase in maximum throughput. PCI Express 2.0 has a signal transfer rate of 5 GT/s, which means the throughput is 500 MB/s for each line. Thus, the main PCI Express 2.0 graphics slot, which typically uses 16 lanes, provides bidirectional throughput of up to 8 GB/s.

With PCI Express 3.0 we will get double these figures. PCI Express 3.0 uses a signal speed of 8 GT/s, which gives a throughput of 1 GB/s per lane. Thus, the main video card slot will receive a throughput of up to 16 GB/s.

At first glance, increasing the signal speed from 5 GT/s to 8 GT/s does not seem like a doubling. However, the PCI Express 2.0 standard uses an 8b/10b encoding scheme, where 8 bits of data are transferred as 10-bit characters for the error correction algorithm. As a result, we get 20% redundancy, that is, a reduction in useful throughput.

PCI Express 3.0 moves to a much more efficient 128b/130b encoding scheme, eliminating 20% ​​redundancy. Therefore, 8 GT/s is no longer a “theoretical” speed; This is an actual rate comparable in performance to the 10 GT/s signal rate if the 8b/10b encoding principle were used.

We asked Jans about devices that will require an increase in speed. He replied that they would include "PLX switches, 40 Gbps Ethernet controllers, InfiniBand, solid state devices, which are becoming increasingly popular, and, of course, video cards." He added, "We haven't run out of innovations, they don't happen statically, they're a continuous stream," paving the way for further improvements in future versions of the PCI Express interface.

Analysis: Where will we use PCI Express 3.0?

Drives

AMD has already integrated support for SATA 6 Gb/s into its 8th line of chipsets, and motherboard manufacturers are adding USB 3.0 controllers. Intel is a little behind in this area, since it does not support USB 3.0 or SATA 6 Gb/s in its chipsets (we already have preliminary samples of P67 motherboards in our laboratory, and they have support for SATA 6 Gb/s, but USB 3.0 in this generation we will not receive). However, as we have repeatedly seen in the confrontation between AMD and Intel, AMD's innovations often inspire Intel. Given the interface speeds of next-generation drives and peripherals, there is no need yet to migrate any of the technologies to PCI Express 3.0. For both USB 3.0 (5 Gbit/s) and SATA 6 Gbit/s (no drives have yet appeared that would fit the limits of this interface), one PCI Express line of the second generation will be sufficient.

Of course, when it comes to drives, the interaction between drives and controllers is only part of the story. Imagine an array of multiple SATA 6 Gb/s SSDs at the chipset, where the RAID 0 array could potentially load the single Gen 2 PCI Express lane that most motherboard manufacturers use to connect the controller. So you can decide whether USB 3.0 and SATA 6 Gb/s interfaces can really require PCI Express 3.0 support after some simple calculations.

As we already mentioned, the USB 3.0 interface gives a maximum speed of 5 Gbps. But like the PCI Express 2.1 standard, USB 3.0 uses 8b/10b encoding, which means the actual peak speed is 4 Gbps. Divide the bits by eight to convert to bytes, and you get a peak throughput of 500 MB/s - exactly the same as a single lane of the current PCI Express 2.1 standard. SATA 6 Gb/s operates at 6 Gb/s, but it also uses an 8b/10b encoding scheme, which turns the theoretical 6 Gb/s into an actual 4.8 Gb/s. Again, convert this value to bytes and you get 600 MB/s, or 20% more than a PCI Express 2.0 lane can provide.

However, the problem lies in the fact that even the fastest SSDs today cannot fully load a SATA 3 Gb/s connection. The peripherals do not even come close to the load of the USB 3.0 interface, the same can be said about the latest generation of SATA 6 Gb/s. At least today, the PCI Express 3.0 interface is not necessary for its active promotion in the platform market. But let's hope that as Intel moves to producing third-generation NAND flash memory, clock speeds will increase and we'll get devices capable of exceeding the 3 Gbps level of second-generation SATA ports.

Video cards

We conducted our own research on the impact of PCI Express bandwidth on video card performance - after PCI Express 2.0 entered the market , at the beginning of 2010, and also recently. We've found that it's very difficult to load the x16 bandwidth currently available on PCI Express 2.1 motherboards. You'll need a multi-GPU setup or an extreme high-end graphics card on a single GPU to be able to tell the difference between x8 and x16 connections.

We asked AMD and Nvidia to comment on the need for PCI Express 3.0 - will this speedy bus be required to unlock the full performance potential of next-generation graphics cards? An AMD spokesperson told us they couldn't comment at this time.

An Nvidia spokesperson was more accommodating: "Nvidia played a key industry role in the development of PCI Express 3.0, which is expected to double the throughput of the current generation (2.0) standard. When significant increases in throughput like this occur, applications emerge that can "Consumers and professionals will benefit from the new standard with increased graphics and compute performance in GPU-equipped laptops, desktops, workstations and servers."

Perhaps the key phrase is “there will be applications that can use them.” It looks like nothing is getting smaller in the graphics world. Displays are getting larger, high resolution is replacing standard definition, and textures in games are becoming more detailed and intriguing. Today we don't believe that even the latest high-end graphics cards have a need to use a PCI Express 3.0 interface with 16 lanes. But year after year, enthusiasts see history repeating itself as advances in technology pave the way for new ways to harness “thicker pipes.” We may see an explosion of applications that will make GPU computing more mainstream. Or, perhaps, the drop in performance that is observed when the video card memory goes beyond the limits, when swapping from system memory begins, will no longer be so noticeable in mass-market and low-end products. In any case, we will have to see the innovations that PCI Express 3.0 will allow AMD and Nvidia to implement.

Motherboard Component Connections

AMD and Intel are always very reluctant to share information about the interfaces they use to connect chipset components or logical “bricks” in the north/south bridges. We know the speed at which these interfaces operate and that they are designed to avoid creating bottlenecks as much as possible. Sometimes we know who made a certain part of the system logic, for example, AMD used a SATA controller based on Silicon Logic design in the SB600. But the technologies used to bridge the gaps between components often remain blind spots. PCI Express 3.0 certainly seems like a very attractive solution, similar to the A-Link interface that AMD uses.

The recent appearance of USB 3.0 and SATA 6 Gb/s controllers on a large number of motherboards also allows us to assess the situation. Since the Intel X58 chipset does not provide native support for either of the two technologies, companies such as Gigabyte have to integrate controllers onto motherboards using available lines to connect them.

The Gigabyte EX58-UD5 motherboard does not support either USB 3.0 or SATA 6 Gb/s. However, it does have a x4 PCI Express slot.

Gigabyte has replaced the EX58-UD5 motherboard with the new X58A-UD5, which has support for two USB 3.0 ports and two SATA 6 Gbps ports. Where did Gigabyte find the bandwidth to support these two technologies? The company took one PCI Express 2.0 line for each controller, reducing the ability to install expansion cards, but at the same time enriching the functionality of the motherboard.

Other than the addition of USB 3.0 and SATA 6Gbps, the only noticeable difference between the two motherboards is the removal of the x4 slot.

Will the PCI Express 3.0 interface, like the standards before it, allow future technologies and controllers to be added to motherboards that will not be present in the current generations of chipsets in an integrated form? It seems to us that it will be so.

CUDA and parallel computing

We are entering the era of desktop supercomputing. Our systems are powered by parallel-intensive graphics processors, power supplies and motherboards capable of supporting up to four graphics cards simultaneously. Nvidia CUDA technology allows you to transform a video card into a tool for programmers to perform calculations not only in games, but also in scientific fields and engineering applications. The programming interface has already proven itself well in developing a variety of solutions for the corporate sector, including image processing in medicine, mathematics, oil and gas exploration work.

We asked the opinion of OpenGL programmer Terry Welsh from the company Really Slick Screensavers about PCI Express 3.0 and GPU computing. Terry told us that "PCI Express has taken a nice leap, and I like that developers are doubling the bandwidth whenever they want - like with version 3.0. However, in the projects I work on, I don't expect to see any difference. Most My work is related to flight simulators, but they tend to be limited by memory and hard drive I/O performance; the graphics bus is not a bottleneck at all, but I can easily foresee that PCI Express 3.0 will provide a significant advance for that. areas of GPU computing; for people who do scientific work with large amounts of data."

The ability to double data transfer rates when running math-intensive workloads is certainly motivating the development of CUDA and Fusion. And this is one of the most promising areas for the upcoming PCI Express 3.0 interface.

Any gamer with an Intel P55 chipset can talk about the advantages and disadvantages of the Intel P55 compared to the Intel X58 chipset. Advantage: Most P55 chipset motherboards are more reasonably priced than Intel X58 models (in general, of course). Disadvantage: the P55 has minimal PCI Express connectivity; the main task is assigned to Intel Clarkdale and Lynnfield processors, which have 16 second-generation PCIe lanes in the CPU itself. Meanwhile, the X58 boasts 36 PCI Express 2.0 lanes.

For P55 buyers who wish to use two graphics cards, they will have to be connected via x8 lanes each. If you want to add a third video card to the Intel P55 platform, you will have to use chipset lines - but, unfortunately, they are limited by the speed of the first generation, and the chipset can allocate a maximum of four lines for an expansion slot.

When we asked PCI-SIG's Al Jans how many lanes we could expect in PCI Express 3.0-enabled chipsets from AMD and Intel, he said it was "proprietary information" that he "cannot disclose." Of course, we did not expect to receive an answer, but it was still worth asking the question. However, it is unlikely that AMD and Intel, which are part of the PCI-SIG Board of Directors, would have invested time and money in PCI Express 3.0 if they planned to use the new PCI Express standard simply as a means of reducing the number of lanes. It seems to us that in the future, AMD and Intel chipsets will continue to be segmented in the same way as we see today, high-end platforms will have enough capabilities to connect a pair of video cards with a full x16 interface, and the number of lines will be reduced for mass market chipsets.

Imagine a chipset similar to the Intel P55, but with 16 PCI Express 3.0 lanes available. Since these 16 lanes are twice as fast as PCI Express 2.0, we get the equivalent of 32 lanes of the old standard. In such a situation, it will be up to Intel whether it wants to make the chipset compatible with 3-way and 4-way GPU configurations. Unfortunately, as we already know, the next generation Intel P67 and X68 chipsets will be limited to PCIe 2.0 support (and Sandy Bridge processors will be similarly limited to supporting 16 lanes on the chip).

In addition to CUDA/Fusion parallel computing, we are also seeing an increase in the capabilities of mass market systems due to the increased communication speed of PCI Express 3.0 components - we think there is considerable potential here too. Without a doubt, PCI Express 3.0 will improve the capabilities of low-cost motherboards, which in the previous generation were only available to high-end platforms. And high-end platforms that have PCI Express 3.0 at their disposal will allow us to set new performance records thanks to innovations in graphics, storage and networking technologies that can use the available bus bandwidth.

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

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

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

Definition

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

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

Using a serial connection, these peripherals are connected to the computer.

The main characteristic of such a device is its throughput.

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

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

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

Specifications

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

It was written above about the exceptional importance of device throughput for its normal functioning.

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

It is capable of simultaneous bidirectional (from card to peripheral and from peripheral to card) equipment connection.

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

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

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

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

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

This directly depends on how many you plan to connect to the motherboard - the more there are, the higher the bandwidth the device needs to maintain stable operation of the computer.

Encryption

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

This protection method is designated 8V/10V.

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

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

Story

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

But, at some point, the maximum technically possible performance was reached and the need arose to create a new type of adapter.

And soon PCI-E appeared - it was 2002.

Immediately there was a need for an adapter that would allow installing new graphics solutions into an outdated expansion slot or vice versa.

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

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

But the development was not successful, since at that time they cost almost the same as the first adapters, and therefore there was a need to develop a simpler adapter configuration.

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

At the same time, slots with different transmission speeds are compatible with any devices of a lower “high-speed” level.

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

Differences between PCI and PCI-E

What specific differences do these two configurations have?

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

While PCI provides parallel information transfer, PCI-E provides serial information transfer, thereby achieving significantly higher information transfer speeds and performance, even taking into account the use of an adapter.

Why is it needed?

Why do you need such an adapter and what can it be used for? Is it possible to do without it?

You need to understand that most users do without this equipment because it is not necessary even on old computers that are subject to significant wear and tear.

This is additional equipment that, in some cases, improves the functionality of your PC, but which the average user can easily do without.

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

It is also quite a convenient option to quickly turn off all peripheral devices at the same time if necessary.

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

PCI - Express (PCIePCI -E)– serial, universal bus first unveiled July 22, 2002 of the year.

Is general, unifying a bus for all nodes of the system board, in which all devices connected to it coexist. Came to replace an outdated tire PCI and its variations AGP, due to increased requirements for bus throughput and the inability to improve the speed performance of the latter at reasonable cost.

The tire acts as switch, simply sending a 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.

Data on the bus 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 (as a direct current, or a bit signal of zeros).

Synchronization constructed using a redundant method. That is, instead of 8 bit information is transmitted 10 bits, two of which are official (20% ) and serve in a certain sequence beacons For synchronization clock generators or identifying errors. Therefore, the declared speed for one line in 2.5 Gbits, is actually equal to 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 sending a signal) lower its clock generator and put the bus into mode reduced energy consumption. If no signal is received within a few microseconds, the device considered inactive and switches to mode expectations(time depends on device type).

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 Gbps

*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). Also improved point-to-point communication protocol(dot-to-dot), modified software component and added system software monitoring according to the tire speed. At the same time, it was preserved 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 official), will apply 130 bit (128 bit information, 2 bits official). 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 expected to increase 2 times(compared to PCI-E 2.0), wherein compatibility will remain with previous versions PCI-Express.

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. 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.

What are the differences between PCI Express and PCI

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 PCI Express device is connected to a common switch with a separate connection.

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

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 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 a x1 connector into a x16 slot on the motherboard.

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

If you need help choosing a video card, call us and we will help!