Almost all modern motherboards currently have 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 his background of appearance, technical specifications and possible modes of operation that will be discussed later.
History of the expansion slot
In the early 2000s, with the AGP expansion slot, which at that time was used to install discrete graphics cards, there was a situation where the maximum level of performance was reached and its capabilities were no longer enough. As a result of this, 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 creative work was the first PCI Express 16x 1.0 specification in 2002.
To ensure compatibility of the two discrete graphics cards installation ports that existed at that time, some companies developed special devices that allowed installing outdated graphics solutions into a new expansion slot. In the language of professionals, this development had its name - the PCI-E x16 / AGP adapter. Its main purpose is to minimize the cost of upgrading a PC by using components from the previous system unit configuration. But this practice is not widespread for the reason that entry-level video cards on the new interface had a cost almost equal to the price of the 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 differed significantly. If AGP and PCI could boast of parallel transmission of information, then PCI Express was a serial interface. Its higher performance was provided by a significantly increased data transfer rate in duplex mode (information in this case could be transmitted simultaneously in two directions).
Baud Rate and Encryption Method
In the designation of the PCI-E x16 interface the number indicates the number of bands used for data transmission. In this case, there are 16. Each of them, in turn, consists of 2 pairs of wires for transmitting information. As noted, a higher speed is ensured by the fact that these pairs operate in duplex mode. That is, information can be transmitted 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 decrypted as follows: for the correct and correct transmission of 8 data bits, it is necessary to supplement them with 2 service bits to perform the validation. In this case, the system is forced to transmit 20 percent of service information, which for the computer user does not carry a payload. But this is a fee for reliable and stable operation of the graphics subsystem of a personal computer, and certainly you can not 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 can vary significantly. As a result, the performance of the device is also different. And the modifications to this graphical interface are as follows:
- 1st PCI modification - Express x16 v. 1.0 had a theoretical throughput of 8 Gb / s.
- 2nd generation PCI - Express x16 v. 2.0 already boasted a doubled bandwidth value of 16 Gb / s.
- A similar trend has been preserved for the third version of this interface. In this case, this indicator was set at around 64 Gb / s.
It is impossible to visually distinguish by the location of the contacts
these slots . Moreover, they are compatible with each other. For example, if you install a graphics adapter board in the version 3.0 slot that meets the physical specifications 2.0, then the entire
graphic information processing system will automatically switch to the lowest speed mode (i.e. 2.0) and will continue to operate with a maximum capacity of 64 GB /from.
First Generation PCI Express
As noted earlier, PCI Express was first introduced in 2002. Its output marked the emergence of personal computers with several graphic adapters, which also boasted even with one accelerator installed increased speed. The AGP 8X standard allowed for a throughput of 2.1 Gb / s, and the first revision of PCI Express - 8 Gb / s.
Of course, talking about an eight-fold increase is not necessary. 20 percent of the increase was used to transfer service information, which allowed to find errors.
The second modification of PCI-E
The first generation of this graphical interface was replaced in 2007 by PCI-E 2. 0 x16. Video cards of the 2nd generation, as noted earlier, were physically and software compatible with the first modification of this interface. Only in this case the graphics system performance 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 was spent on official information. As a result, in the first case, the real transfer was equal to: 8 Gb / s - (8 Gb / s x 20%: 100%) = 6.4 Gb / s. And for the second execution 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 speed by 2 times between the 1st and 2nd PCI Express versions.
Third generation
The latest and most current update to this interface was released in 2010. The peak speed of PCI-E x16 in this case increased to 64 Gb / s, and the maximum power of the graphics adapter without additional power in this case can be equal to 75 watts.
Configuration options with multiple graphic accelerators as part of a single PC. Their pros and cons
One of the most important innovations of this interface is the possibility of having several graphic adapters in the PCI-E x16 buses at once. The video cards are combined with each other and form, in essence, a single device. Their overall performance is summarized, and this allows to significantly increase the speed of the PC from the position of processing the output image. For NVidia solutions, this mode is called SLI, and for AMD GPUs, it is called CrossFire.
The future of this standard
PCI-E x16 slot in the foreseeable future certainly will not change. This will allow more efficient video cards to be used as part of outdated PCs and, due to this, carry out a phased upgrade of a computer system. Now specifications for the 4th version of this data transfer method are already being worked out. For graphics cards in this case, a maximum bandwidth of 128 Gb / s will be provided. This will allow you to display the image on the monitor screen as "4K" or more.
Summary
Be that as it may, the PCI-E x16 is currently a non-alternative graphics slot and interface. It will be relevant for quite some time. Its parameters allow you to create both entry-level computer systems and high-performance PCs with several accelerators. It is due to such flexibility that no significant changes are expected in this niche.