What is the difference between the pci e. Expansion slot. Differences PCI Express from PCI

In the spring of 1991, Intel completed the development of the first prototype PCI bus. The engineers were tasked with developing an inexpensive and productive solution that would allow the 486, Pentium and Pentium Pro processors to be realized. In addition, it was necessary to take into account the mistakes made by VESA when designing the VLB bus (the electrical load did not allow connecting more than 3 expansion cards), and also to implement automatic device configuration.

In 1992, the first version of the PCI bus appears, Intel announces that the bus standard will be open, and creates the PCI Special Interest Group. Thanks to this, any interested developer gets the opportunity to create devices for the PCI bus without the need to purchase a license. The first version of the bus had a clock frequency of 33 MHz, it could be 32- or 64-bit, and the devices could work with signals of 5 V or 3.3 V. Theoretically, the bus bandwidth is 133 MB / s, but in reality the bandwidth was about 80 MB / s.

Main characteristics:

• bus frequency - 33.33 or 66.66 MHz, synchronous transmission;
• bus width - 32 or 64 bits, multiplexed bus (address and data are transmitted over the same lines);
• peak bandwidth for the 32-bit version, operating at 33.33 MHz - 133 MB / s;
• memory address space - 32 bits (4 bytes);
• address space of input-output ports - 32 bits (4 bytes);
• configuration address space (for one function) - 256 bytes;
• voltage - 3.3 or 5 V.

Photo of connectors:

MiniPCI - 124 pin
MiniPCI Express MiniSata / mSATA - 52 pin
Apple MBA SSD, 2012
Apple SSD, 2012
Apple PCIe SSD
MXM, Graphics Card, 230/232 pin
MXM2 NGIFF 75 pins KEY A PCIe x2 KEY B PCIe x4 Sata SMBus
MXM3, Graphics Card, 314 pin
PCI 5V
PCI Universal
PCI-X 5v
AGP Universal
AGP 3.3 v
AGP 3.3 v + ADS Power
PCIe x1
PCIe x16
Custom PCIe
ISA 8bit
ISA 16bit
eISA
VESA
NuBus
PDS
PDS
Apple II / GS Expasion slot
PC / XT / AT expasion bus 8 bit
ISA (industry standard architecture) - 16 bit
eISA
MBA - Micro Bus architecture 16 bit
MBA - Micro Bus architecture with 16 bit video
MBA - Micro Bus architecture 32 bit
MBA - Micro Bus architecture with 32 bit video
ISA 16 + VLB (VESA)
Processor Direct Slot PDS
601 Processor Direct Slot PDS
LC Processor Direct Slot PERCH
NuBus
PCI (Peripheral Computer Interconnect) - 5v
PCI 3.3v
CNR (Communications / network Riser)
AMR (Audio / Modem Riser)
ACR (Advanced communication Riser)
PCI-X (PCI Peripheral) 3.3v
PCI-X 5v
PCI 5v + RAID option - ARO
AGP 3.3v
AGP 1.5v
AGP Universal
AGP Pro 1.5v
AGP Pro 1.5v + ADC power
PCIe (peripheral component interconnect express) x1
PCIe x4
PCIe x8
PCIe x16

PCI 2.0

The first version of the basic standard, which became widespread, used both cards and slots with a signal voltage of only 5 volts. Peak throughput - 133 MB / s.

PCI 2.1 - 3.0

They differed from version 2.0 by the possibility of simultaneous operation of several bus masters (English bus-master, the so-called competitive mode), as well as by the appearance of universal expansion cards capable of operating both in slots using a voltage of 5 volts and in slots using 3 , 3 volts (with a frequency of 33 and 66 MHz, respectively). Peak throughput for 33 MHz is 133 MB / s, and for 66 MHz it is 266 MB / s.

• Version 2.1 - work with 3.3 volt cards, and the presence of the corresponding power lines were optional.
• Version 2.2 - expansion cards made in accordance with these standards have a universal power connector key and are able to work in many later varieties of PCI bus slots, as well as, in some cases, in version 2.1 slots.
• Version 2.3 is incompatible with PCI cards rated for 5 volts, despite the continued use of 32-bit slots with a 5-volt key. Expansion cards have a universal connector, but they are not able to work in 5-volt slots of earlier versions (up to 2.1 inclusive).
• Version 3.0 - Completes the transition to 3.3 volt PCI cards, 5 volt PCI cards are no longer supported.

PCI 64

An extension to the base PCI standard introduced in version 2.1 that doubles the number of data lines and therefore the bandwidth. The PCI 64 slot is an extended version of the regular PCI slot. Formally, the compatibility of 32-bit cards with 64-bit slots (provided there is a common supported signal voltage) is complete, and the compatibility of a 64-bit card with 32-bit slots is limited (in any case, performance will be lost). Works at a clock frequency of 33 MHz. Peak throughput is 266 MB / s.

• Version 1 - Uses a 64-bit PCI slot and 5 volts.
• Version 2 - Uses a 64-bit PCI slot and 3.3 volts.

PCI 66

PCI 66 is a 66 MHz evolution of PCI 64; uses 3.3 volts in the slot; the cards have a universal or 3.3V form factor. Peak throughput is 533 MB / s.

PCI 64/66

The combination of PCI 64 and PCI 66 allows up to four times the data transfer rate of the base PCI standard; Uses 64-bit 3.3-volt slots only compatible with universal and 3.3-volt 32-bit expansion cards. PCI64 / 66 cards have either universal (but limited compatibility with 32-bit slots) or 3.3V form factor (the latter option is fundamentally incompatible with 32-bit 33MHz slots of popular standards). Peak throughput - 533 MB / s.

PCI-X

PCI-X 1.0 - expansion of the PCI64 bus with the addition of two new operating frequencies, 100 and 133 MHz, as well as a mechanism for separate transactions to improve performance when multiple devices work simultaneously. Generally backward compatible with all 3.3V and general purpose PCI cards. PCI-X cards usually run in 64-bit 3.3 V format and have limited backward compatibility with PCI64 / 66 slots, and some PCI-X cards are in a universal format and are able to work (although this has almost no practical value) in the usual PCI 2.2 / 2.3. In difficult cases, in order to be completely sure of the functionality of the combination of the motherboard and expansion card, it is necessary to look at the compatibility lists of the manufacturers of both devices.

PCI-X 2.0

PCI-X 2.0 - further expands the capabilities of PCI-X 1.0; added frequencies 266 and 533 MHz, as well as - data transmission parity error correction (ECC). Allows splitting into 4 independent 16-bit buses, which is used exclusively in embedded and industrial systems; the signal voltage has been reduced to 1.5 V, but the connectors are backward compatible with all cards using a signal voltage of 3.3 V. Currently, for the non-professional segment of the market for high-performance computers (powerful workstations and entry-level servers), in which PCI-X bus, very few motherboards with bus support are produced. An example of a motherboard for such a segment is the ASUS P5K WS. In the professional segment, it is used in RAID controllers, in SSD drives for PCI-E.

Mini PCI

Form factor PCI 2.2, designed for use mainly in laptops.

PCI Express

PCI Express, or PCIe, or PCI-E (also known as 3GIO for 3rd Generation I / O; not to be confused with PCI-X and PXI) - computer bus(although it is not a bus at the physical level, being a point-to-point connection) using program model PCI buses and a high-performance physical protocol based on serial data transmission... The development of the PCI Express standard was started by Intel after the abandonment of the InfiniBand bus. Officially, the first basic PCI Express specification appeared in July 2002. PCI Express is being developed by the PCI Special Interest Group.

Unlike the PCI standard, which used a common bus for data transfer with several devices connected in parallel, PCI Express, in general, is a packet network with star topology... PCI Express devices communicate with each other through a switch environment, with each device directly connected through a point-to-point connection to the switch. In addition, the PCI Express bus supports:

• hot swap of cards;
• guaranteed bandwidth (QoS);
• energy management;
• control of the integrity of the transmitted data.

The PCI Express bus is intended to be used only as a local bus. Since the PCI Express software model is largely inherited from PCI, existing systems and controllers can be modified to use the PCI Express bus by replacing only the physical layer, without modifying the software. The high peak performance of the PCI Express bus makes it possible to use it instead of AGP buses, and even more so PCI and PCI-X. De facto PCI Express has replaced these buses in personal computers.

• MiniCard (Mini PCIe) is a replacement for the Mini PCI form factor. The following buses are brought out to the Mini Card slot: x1 PCIe, 2.0 and SMBus.
  • M.2 is the second version of Mini PCIe, up to x4 PCIe and SATA.
• ExpressCard is similar to the PCMCIA form factor. The ExpressCard slot has x1 PCIe and USB 2.0 buses, ExpressCards support hot plugging.
• AdvancedTCA, MicroTCA - form factor for modular telecommunications equipment.
  
• The Mobile PCI Express Module (MXM) is an industrial form factor designed for notebook computers by NVIDIA. It is used to connect graphics accelerators.
• PCI Express cable specifications make it possible to increase the length of one connection to tens of meters, which makes it possible to create a computer, the peripheral devices of which are at a considerable distance.
  
• StackPC is a specification for building stackable computer systems. This specification describes the expansion connectors StackPC, FPE and their mutual arrangement.

Despite the fact that the standard allows x32 lines per port, such solutions are physically rather cumbersome and not available.

PCI Express 2.0

The PCI-SIG released the PCI Express 2.0 specification on January 15, 2007. The main innovations in PCI Express 2.0:

• Increased bandwidth: 500 MB / s single line bandwidth, or 5 GT / s ( Gigatransactions / s).
• Improvements have been made to the transfer protocol between devices and the programming model.
• Dynamic speed control (to control the speed of communication).
• Bandwidth alert (to notify the software about changes in bus speed and width).
• Access Control Services - Optional point-to-point transaction management capabilities.
• Execution timeout control.
• Reset at the function level - an optional mechanism for resetting functions (PCI functions) inside a device (PCI device).
• Override the power limit (to override the slot power limit when connecting devices that consume more power).

PCI Express 2.0 is fully compatible with PCI Express 1.1 (the old ones will work in motherboards with new connectors, but only at 2.5 GT / s, since the old chipsets cannot support double the data transfer rate; new video adapters will work without problems in old PCI Express 1.x slots).

PCI Express 2.1

In terms of physical characteristics (speed, connector) it corresponds to 2.0, in the software part, functions have been added that are fully planned to be introduced in version 3.0. Since most motherboards are sold with version 2.0, the presence of only a video card with 2.1 does not allow using the 2.1 mode.

PCI Express 3.0

PCI Express 3.0 specifications were approved in November 2010. The interface has a baud rate of 8 GT / s ( Gigatransactions / s). But despite this, its real bandwidth was still doubled compared to the PCI Express 2.0 standard. This was achieved thanks to the more aggressive 128b / 130b encoding scheme, where 128 bits of data sent over the bus are encoded with 130 bits. At the same time, full compatibility with previous PCI Express versions has been preserved. PCI Express 1.x and 2.x cards will work in slot 3.0, and conversely, a PCI Express 3.0 card will work in 1.x and 2.x slots.

PCI Express 4.0

The PCI Special Interest Group (PCI SIG) said PCI Express 4.0 could be standardized before the end of 2016, but by mid-2016, with a number of chips in preparation for production, the media reported that standardization was expected in early 2017. will have a bandwidth of 16 GT / s, that is, it will be twice as fast as PCIe 3.0.

Leave your comment!

"Manhunt1908"The motherboard's support for the new PCI Express v.3.0 standard is not really its competitive advantage." We basically get that in PCI Express 3.0, in fact, it has no real advantages, and it will not increase the speed in modern games. then no one needs it and is not interested, there is no gain, which means it sucks, but in addition to the gaming functions of the PCI Express v.3.0 standard, it has other functions, in particular, USB 3.0 directly depends on the motherboard with the PCI Express support function 3.0, they themselves say that, Well, the presence of two or four USB 3.0 ports in a computer, by today's standards, is simply necessary, 3.0 is much faster than 2.0, many have tested this in practice. 3.0 is needed, a lot of the latest technologies are tied to this particular standard. Why would anyone refuse to have such a list below on board their motherboard!
SupremeFX IV
Perfect sound
This motherboard boasts a high-quality audio system based on the built-in SupremeFX IV sound card, which is marked on the PCB with a special line. High-capacity capacitors and electromagnetic shielding contribute to the highest sound quality. In addition, SupremeFX IV includes a dedicated headphone amplifier.

Gamefirst ii
GameFirst II, powered by cFos Traffic Shaping, helps you prioritize Internet bandwidth usage by various applications. Having received the highest priority, online games will work as quickly as possible, without annoying "lags", and other online applications that have a low priority of using the Internet channel will not interfere with them. There is a user-friendly ROG-style GUI to access this feature.

Gigabit Ethernet Controller
Intel network controllers are renowned for their stable and efficient operation at low CPU utilization.

MPCIe Combo adapter and Wi-Fi / Bluetooth 4.0 controller
To save on the main expansion slots, this motherboard is equipped with a special additional slot with an mPCIe Combo adapter, to which you can connect devices with mSATA (for example, solid-state disk) and mPCIe (wireless adapters Wi-Fi, 3G / 4G, GPS, etc.) .). Moreover, the package already includes an mPCIe card with support for Wi-Fi 802.11 a / b / g / n and Bluetooth 4.0.

Fusion Thermo Cooling System
To cool the power system elements on this motherboard, a special ROG Fusion Thermo cooler is used, which consists of a copper water block, massive radiators and a heat pipe. Thus, it can be used as part of a liquid cooling system as well as for conventional cooling with fans. > Learn more
ROG Connect

ROG Connect overclocking and tweaking interface
With the ROG Connect function, you can monitor the status of your computer and adjust its parameters in real time using a laptop, connecting the latter to the main system via a USB cable.

Extreme Engine Digi + II
High efficiency digital power system
The Extreme Engine Digi + II power management system is highly efficient thanks to the variable PWM frequency of the digital voltage regulators in the processor and memory. It also uses high quality Japanese capacitors. A reliable and powerful power supply system is the key to successful computer operation in overclocking mode!

ROG CPU-Z
The new face of the famous utility
ROG CPU-Z is a customized version of the well-known information utility from CPUID. It provides the same functionality and accuracy of information about the system as the original, but has a unique interface in the style of Republic of Gamers. With ROG CPU-Z, you can get complete information about the processor and some other components of your computer.

Multi-GPU technologies
LucidLogix Virtu MVP
High speed in graphics applications
LucidLogix Virtu MVP technology is Windows 7 software that automatically switches between the on-chip graphics and discrete graphics. By putting a discrete video card into sleep mode at those moments when its resources are not needed, energy savings are achieved, the noise level from the computer is reduced and the temperature inside the system unit is reduced, which contributes to a more favorable mode of operation of all components. In addition, you can use the integrated graphics to accelerate the main graphics card, which can increase performance by up to 60% (as measured by 3DMark Vantage benchmarks). It should also be noted that this technology is fully compatible with the Intel Quick Sync 2.0 video transcoding function.

Briefly about history ...

For the first time, a separate interface designed to becomea replacement for the PCI bus for video cards, was introduced in 1997. AGP (Accelerated Graphics Port) - this is how Intel presented its new development simultaneously with the official announcement of the chipset for Intel Pentium II processors.

Declared benefitsAGP before its predecessorPCIwere significant:

• higher operating frequency (66 MHz);
• increased bandwidth between the video card and the system bus;
• direct transfer of information between the video card and RAM, bypassing the processor;
• improved power supply system;
• high-speed access to shared memory.

Due development standardAGP 1x (AGP 1.0 specification) was not received due to the low speed of working with memory and was almost immediately improved, and its speed was doubled - this is how the AGP 2x interface appeared. Transmitting 32 bits (4 bytes) per cycle, the AGP 2x port could deliver a peak performance unprecedented at that time of 66.6x4x2 = 533 MB/ s.

In 1998, the AGP 4x standard (AGP 2.0 specification) was released, which provides the transfer of up to 4 blocks of information per cycle. At the same time, the signal voltage of the port was reduced from 3.3 to 1.5 V. The maximum throughput of AGP 4x became about 1GB/ s... In the future, the development of specifications was protracted - the reason for this was the very low speed of the existing video accelerator fleet at that time, as well as the low speed of exchange with RAM.

As soon as the technical progress "rested" on the bus, which turned out to be too small for the transmission of huge data streams by modern video cards, a new standard was approved - AGP 8x (AGP 3.0 specification). As you might have guessed, it can transmit up to 8 blocks of information per clock cycle and has a peak bandwidth of 2GB/ s... The AGP 8x bus is backward compatible with AGP 4x.

The high-tech industry is always skyrocketing. The volumes of transmitted and transmitted data are increasing, textures and their quality are growing, all this certainly forces each of the manufacturers to shake things up for themselves and produce something new and high-tech (standard, specifications, protocol, interface) that will bind a new round in the spherehi- tech.

Officially, the first basic PCI Express specification appeared in July 2002, thus marking the day of the gradual "death" of AGP 8x ...

Introduction

At the moment, the modern Intel P45 / X48 chipset has official support for PCI Express 2.0 specifications, which the very common Intel P35 could not boast of. For those who are just going to buy a modern motherboard on the Intel platform, the choice remains quite obvious - the P45 / X48 chipset, and you will not face the dilemma of "enough or not enough" PCI Express 1.1 for the current hi-end or middle-end video card. But what about the owners of the P35s? Should I run to the store again?

In our today's material, we will try to dot the "I" regarding the advantages of PCI-E 2.0 over PCI-E 1.1 for modern accelerators. We will also experimentally analyze the performance of video cards when working with various interfaces, on the basis of which a conclusion will be drawn about the practical value of PCI-E 2.0.

And before proceeding with any objective tests, let's delve a little deeper into the theory, namely, we will figure out how it all works in general.

PCI- Express- briefly about the main

As mentioned above, the basic PCI Express specification appeared in July 2002. With its high speed and peak performance, PCI Express leaves no room for its predecessor AGP. In terms of its software model, the new PCI-E interface is in many respects similar to PCI, which makes it easy to adapt the current fleet of all kinds of devices to the new interface without significant software "adjustments".

The principle of operation of PCI Express is based on serial data transmission. The bus is a star topology packet network. PCI-E devices communicate using a bi-directional point-to-point connection called "Line". Each PCI Express connection can consist of one (1x) or multiple lanes (4x, 16x, etc.).

For a basic PCI-Express 1x configuration, the theoretical bandwidth is 250 MB / s in each direction (transmit / receive). Accordingly, for PCI-E x16, this value is 250 MB / s x 16 = 4 GB / s.

It is noteworthy that from the physical side, the interface allows, for example, any motherboard with a PCI-E 1x interface to work confidently not only in the standard one, but also in any other PCI Express slot of higher bandwidth (4x, 16x, etc.). In this case, the maximum number of involved lines depends only on the properties of the device.

In all high-speed protocols, the issue of noise immunity always arises. In this regard, PCI Express uses the well-known scheme of 8/10 or excess traffic (8 bits of data transmitted over the channel are replaced by 10 bits, thus additional information is generated, about 20% of the total "flow").

PCIExpress 2.0

The standard was officially approved on January 15, 2007. In the second revision of PCI Express, the throughput of one channel has significantly increased - up to 5 Gb / s (PCI Express 1.x - 2.5 Gb / s). This means that now for the x16 line the maximum data transfer rate can reach 8 GB / s in both directions versus 4 GB / s for the old PCI Express 1.x.

Notably, PCI Express 2.0 is fully compatible with PCI Express 1.1. In fact, this means that old video cards will work quietly in motherboards with new connectors, and new video adapters will work without problems in old PCI Express 1.x slots.

Perhaps, with this theory and the main features of PCI Express, let's round off, it's time to start the relevant tests, which we, in fact, will do, however, a little below, but for now, let's get to know the test participants in detail.

About test participants

Unfortunately, it was not possible to cover a larger set of graphics accelerators at the time of testing, which we will definitely fix in the future. Low-End video cards were deliberately excluded from the tests, since they are of little use for high-resolution modes (over 1280x1024) with maximum picture detail, where the advantages of PCI-E 2.0 over the junior PCI-E 1.1 can be revealed.

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 capable of transferring 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, 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.

When changing only one video card, be sure to take into account that new models may simply not fit your motherboard, since there are not only several different types of expansion slots, but also several different versions of them (as applied to both AGP and PCI Express). If you are unsure of your knowledge of this topic, please read the section carefully.

As we have already noted above, the video card is inserted into a special expansion slot on the computer's motherboard, through this slot the video chip exchanges information with the central processor of the system. Motherboards often have one or two different types of expansion slots, differing in bandwidth, power supply parameters and other characteristics, and not all of them are suitable for installing video cards. It is important to know the connectors available in the system and buy only the video card that matches them. Different expansion connectors are physically and logically incompatible, and a video card designed for one type will not fit into another and will not work.

Fortunately, not only ISA and VESA Local Bus expansion slots (which are of interest only to future archaeologists) and their corresponding video cards have fallen into oblivion over the past time, but video cards for PCI slots have also practically disappeared, and all AGP models are hopelessly outdated. And all modern GPUs use only one type of interface - PCI Express. Previously, the AGP standard was widespread, these interfaces differ significantly from each other, including the bandwidth, the capabilities provided for powering the video card, as well as other less important characteristics.

Only a very small part of modern motherboards do not have PCI Express slots, and if your system is so old that it uses an AGP video card, then you will not be able to upgrade it - you need to change the entire system. Let's take a closer look at these interfaces; these are the slots you need to look for on your motherboards. See photos and compare.

AGP (Accelerated Graphics Port or Advanced Graphics Port) is a high-speed interface based on the PCI specification, but designed specifically for connecting video cards and motherboards. Although the AGP bus is better suited for video adapters than PCI (not Express!), It provides a direct connection between the central processor and the video chip, as well as some other features that increase performance in some cases, for example, GART - the ability to read textures directly from RAM without copying them into video memory; a higher clock frequency, simplified data transfer protocols, etc., but this type of slots is hopelessly outdated and new products with it have not been released for a long time.

But still, for the sake of order, we will also mention this type. AGP specifications appeared in 1997, then Intel released the first version of the description, which included two speeds: 1x and 2x. In the second version (2.0) AGP 4x appeared, and in 3.0 - 8x. Let's consider all the options in more detail:
AGP 1x is a 32-bit channel operating at 66 MHz with a bandwidth of 266 MB / s, which is twice the PCI bandwidth (133 MB / s, 33 MHz and 32 bits).
AGP 2x is a 32-bit channel operating with twice the bandwidth of 533 MB / s at the same frequency of 66 MHz due to data transfer on two edges, similar to DDR memory (only for the direction "to the video card").
AGP 4x is the same 32-bit channel operating at 66 MHz, but as a result of further tweaks, a quadruple "effective" frequency of 266 MHz was achieved, with a maximum bandwidth of more than 1 GB / s.
AGP 8x - additional changes in this modification made it possible to get the bandwidth up to 2.1 GB / s.

AGP video cards and corresponding slots on motherboards are compatible within certain limits. Graphics cards rated for 1.5V do not work in 3.3V slots and vice versa. However, there are also universal connectors that support both types of boards. Video cards designed for a morally and physically outdated AGP slot have not been considered for a long time, so to learn about old AGP systems, it would be better to read the article:

PCI Express (PCIe or PCI-E, not to be confused with PCI-X), formerly known as Arapahoe or 3GIO, differs from PCI and AGP in that it is a serial rather than parallel interface, which reduces the number of pins and increases bandwidth. PCIe is just one example of the shift from parallel to serial buses, other examples of this movement are HyperTransport, Serial ATA, USB and FireWire. An important advantage of PCI Express is that it allows multiple single lanes to be stacked into a single lane to increase bandwidth. The multichannel sequential design increases flexibility, slower devices can be assigned fewer lines with fewer pins, and faster ones more.

PCIe 1.0 transfers data at 250 MB / s per lane, nearly double the capacity of conventional PCI slots. The maximum number of lanes supported by PCI Express 1.0 slots is 32, which gives a bandwidth of up to 8 GB / s. And the PCIe slot with eight working lanes is roughly comparable in this parameter with the fastest AGP version - 8x. Which is even more impressive when you consider the possibility of simultaneous transmission in both directions at high speed. The most common PCI Express x1 slots provide bandwidth of one lane (250 MB / s) in each direction, and PCI Express x16, which is used for video cards and which combines 16 lanes, provides bandwidth up to 4 GB / s in each direction.

Despite the fact that the connection between two PCIe devices is sometimes assembled from several lines, all devices support a single line, at least, but can optionally work with a large number of them. Physically, PCIe expansion cards go in and work fine in any slots with equal or more lanes, so a PCI Express x1 card will work fine in x4 and x16 slots. Also, a physically larger slot can work with a logically fewer lines (for example, a seemingly ordinary x16 connector, but only 8 lines are routed). In any of the above options, PCIe will choose the highest possible mode by itself, and it will work fine.

Most often, x16 connectors are used for video adapters, but there are boards with x1 connectors. Most motherboards with two PCI Express x16 slots operate in x8 mode to create SLI and CrossFire systems. Physically, other slot options such as x4 are not used for video cards. Let me remind you that all this applies only to the physical layer, there are also motherboards with physical PCI-E x16 slots, but in reality with 8, 4 or even 1 channels. And any video cards designed for 16 channels will work in such slots, but with lower performance. By the way, the photo above shows the x16, x4 and x1 slots, and for comparison, PCI is also left (below).

Although the difference in games is not that big. For example, here is a review of two motherboards on our website, which examines the difference in the speed of 3D games on two motherboards, a pair of test video cards in which operate in 8-channel and 1-channel modes, respectively:

The comparison that interests us is at the end of the article, pay attention to the last two tables. As you can see, the difference at medium settings is quite small, but in heavy modes it starts to increase, and a big difference was noted in the case of a less powerful video card. Take note of this.

PCI Express differs not only in bandwidth, but also in new power consumption capabilities. This need arose because the AGP 8x slot (version 3.0) can only transfer no more than 40-plus watts in total, which was no longer enough for video cards of the then generations designed for AGP, on which one or two standard four-pin power connectors were installed. A PCI Express slot can carry up to 75W, and an additional 75W is received over a standard six-pin power connector (see the last section of this part). Recently, video cards with two such connectors have appeared, which in total gives up to 225 watts.

Subsequently, the PCI-SIG group, which develops the corresponding standards, presented the main PCI Express 2.0 specifications. The second version of PCIe doubles the standard bandwidth, from 2.5 Gbps to 5 Gbps, so the x16 connector can transfer data at speeds up to 8 GB / s in each direction. At the same time, PCIe 2.0 is compatible with PCIe 1.1, old expansion cards usually work fine in new motherboards.

The PCIe 2.0 specification supports both 2.5 Gb / s and 5 Gb / s transfer rates to ensure backward compatibility with existing PCIe 1.0 and 1.1 solutions. PCI Express 2.0 backward compatibility allows legacy 2.5 Gbps solutions in 5.0 Gbps slots, which would simply operate at a lower speed. And devices designed to specification version 2.0 can support speeds of 2.5 Gbps and / or 5 Gbps.

Although the main innovation in PCI Express 2.0 is the speed doubled to 5 Gb / s, but this is not the only change, there are other modifications to increase flexibility, new mechanisms for programmatically controlling the connection speed, etc. We are most interested in changes related to with power supply of devices, as the power requirements of video cards are steadily growing. PCI-SIG has developed a new specification to accommodate the increasing power consumption of graphics cards, which expands the current power supply capabilities to 225/300 watts per graphics card. To support this specification, a new 2 × 4-pin power connector is used to provide power to high-end graphics cards.

Video cards and mainboards with PCI Express 2.0 support appeared on the market already in 2007, and now there are no others on the market. Both major video chip manufacturers, AMD and NVIDIA, have released new lines of GPUs and video cards based on them, supporting the increased bandwidth of the second version of PCI Express and taking advantage of new power supply options for expansion cards. All of them are backward compatible with motherboards with PCI Express 1.x slots, although incompatibilities are observed in some rare cases, so you need to be careful.

Actually, the appearance of the third version of PCIe was an obvious event. In November 2010, the specifications for the third version of PCI Express were finally approved. Although this interface has a transfer rate of 8 Gt / s instead of 5 Gt / s in version 2.0, its bandwidth has doubled again compared to the PCI Express 2.0 standard. To do this, we used a different encoding scheme for the data sent over the bus, but at the same time, compatibility with previous versions of PCI Express was preserved. The first products of the PCI Express 3.0 version were presented in the summer of 2011, and real devices have just begun to appear on the market.

A war broke out among motherboard manufacturers for the right to be the first to present a product with PCI Express 3.0 support (mainly based on the Intel Z68 chipset), and several companies presented the corresponding press releases at once. Although at the time of the update of the guide, there are simply no video cards with such support, so it's just not interesting. By the time PCIe 3.0 support is needed, completely different boards will appear. Most likely, this will not happen until 2012.

By the way, we can assume that PCI Express 4.0 will be presented in the next few years, and the new version will also have doubled the bandwidth demanded by that time. But this will not happen very soon, and we are not interested in it yet.

External PCI Express

In 2007, the PCI-SIG group, which officially standardizes PCI Express solutions, announced the adoption of the PCI Express External Cabling 1.0 specification, which describes the PCI Express 1.1 external interface data transfer standard. This version allows data transfer at a speed of 2.5 Gbps, and the next one should increase the bandwidth to 5 Gbps. The standard provides four external slots: PCI Express x1, x4, x8 and x16. Older connectors are equipped with a special tongue to facilitate connection.

The external version of the PCI Express interface can be used not only for connecting external video cards, but also for external drives and other expansion cards. The maximum recommended cable length is 10 meters, but it can be increased by connecting the cables through a repeater.

In theory, this could make life easier for laptop enthusiasts when running on battery power using a low-power integrated video core, and when connected to a desktop monitor, a powerful external video card. The upgrade of such video cards is greatly facilitated; there is no need to open the PC case. Manufacturers can make completely new cooling systems that are not limited by the features of expansion cards, and there should be fewer problems with power supply - most likely, external power supplies designed specifically for a specific video card will be used, they can be built into one external case with a video card, using one cooling system. It may be easier to assemble systems on several video cards (SLI / CrossFire), and given the constant growth in the popularity of mobile solutions, such external PCI Express should have gained some popularity.

They should have, but they did not win. As of autumn 2011, there are practically no external versions of video cards on the market. Their circle is limited to outdated models of video chips and a narrow selection of compatible laptops. Unfortunately, the business of external video cards did not go any further, and slowly died out. Even victorious advertising announcements from laptop manufacturers are no longer heard ... Perhaps, the capacities of modern mobile video cards simply began to suffice even for demanding 3D applications, including many games.

There remains hope for the development of external solutions in the promising interface for connecting Thunderbolt peripherals, formerly known as Light Peak. It was developed by Intel Corporation based on DisplayPort technology, and the first solutions have already been released by Apple. Thunderbolt combines DisplayPort and PCI Express capabilities and allows you to connect external devices. However, so far those simply do not exist, although the cables already exist:

In this article, we do not touch on outdated interfaces, the vast majority of modern video cards are designed for the PCI Express 2.0 interface, therefore, when choosing a video card, we suggest considering only it, all data on AGP are provided for reference only. The new boards use PCI Express 2.0 interface, combining the speed of 16 PCI Express lanes, which gives up to 8 GB / s throughput in each direction, which is several times more than the same characteristic of the best AGP. In addition, PCI Express operates at this speed in each direction, unlike AGP.

On the other hand, products with PCI-E 3.0 support have not really come out yet, so it doesn't make much sense to consider them either. If we are talking about upgrading an old or buying a new motherboard or simultaneously changing the system and video cards, then you just need to purchase cards with the PCI Express 2.0 interface, which will be quite sufficient and most widespread for several more years, especially since products of different PCI Express versions are compatible with each other. ...