Today our topic is the PCI-E interface. It may be the largest interface as the motherboard. Its application range is very broad, not only for the discrete graphics card we often use, other devices such as NIC video capture cards are also passed by PCI -E standard is used.
The PCI-E interface is a relatively universal interface standard on the motherboard. It is mainly provided to use equipment that needs to communicate directly with the CPU. It is usually necessary to expand the functionally supported function on the motherboard, such as an extension of the discrete graphics, etc. Platform outputs more powerful graphics capabilities to make up for the shortcomings of the nuclear.
PCI-E Interface of DIS
In recent hours, you may have heard more about the solid state drive of the PCI-E interface, or the solid state drive of the M.2 interface, as long as the SSD product supporting the NVME protocol is through the PCI-E bus. The processor interaction, the highest supports to the bandwidth of PCI-E 3.0 X4, and the author will explain later.
PCI interface
The PCI bus is known as Peripheral Component Interconnect, translated into Chinese is a "peripheral device interconnection", which is a local parallel bus standard introduced by PCI Special Interest Group. The PCI bus standard is developed in 1992. It is a big age than the little wolf. His appearance is developed by the ISA (INDUSTY STANDARD ARCHITECT) bus.
PCI interface
The ordinary PCI interface data width is 32 bits (Bit, that is, the small b), the interaction speed is 33MHz, the theory's maximum bandwidth is 4Byte / s * 33MHz = 133MB / s, note that this will become byte byte, That is, the big B, because the data in the computer is calculated in binary, so 33MHz in this equation should be 33.33333 ....
PCI (on) and PCI-X (below)
The PCI-X of the higher transmission speed of the later launched is still adopted by the PCI bus standard, and the speed of the pins is increased, and the new PCI 64/66 provides 64-bit (BIT) data width and 66MHz operating frequency. The theoretical bandwidth is increased to 533MB / s. This idea seems to be used in combination of two PCI interfaces, but not exactly the same.
AGP interface
AGP (Accelerated Graphics Port) is developed based on the PCI bus, which is specifically launched for increasing image processing requirements, but the main purpose it appears to solve the display card and processor Communication issues, so it is just a "port", "which means it can only connect a terminal and this terminal must be a graphic accelerator card. PCI is a bus, which can connect many different types of terminals, which can be The graphics card can also be a network card or a SCSI card, there is a sound card, and so on. "(Cited Baidu Baibo, AGP slot entry)
AGP interface
The AGP is used along the PCI specification, 32-bit data width, but the operating frequency begins with 66MHz, and the AGP1x specification provides 266MB / s theoretical bandwidth. The version of the AGP2X has adopted a new two-way data transmission technology (the rising edge and the falling edge transmits a data), so that the theoretical bandwidth doubles, reaching 533MB / s.
After the segmentation requirements of the screen, the bandwidth of the AGP2X is not enough, and the AGP4X is born, the operating frequency is not changed, and the theoretical bandwidth is doubled, and the theoretical bandwidth is doubled, and it is increased to 1066Mb / s. In the later stage, the AGP8X version will double the bandwidth again, reaching 2133MB / s.
AGP interface coexisting in the later and PCI-E interface
In the later, the high-occupied defects in AGP highlighted, and the bandwidth increased gradually. In 2002, PCI Express is also confirmed by the PCI-E standard, but because the price of the original start, there is a motherboard to carry AGP and The case of the PCI-E interface, for a long time, the user still insists on selecting the AGP graphics card to install.
PCI-E interface
Finally, the top of the top, the PCI-E interface, which is currently using the most widely used general interface, with bandwidth is divided into 1x / 2x / 4x / 8x / 16x. At present, there are very few other interfaces on the motherboard, mainly PCI-E. Extended interfaces, 2x slots are also relatively rare.
The PCI-E interface changes the parallel data transmission mode used by PCI and AGP to a serial transmission. The advantages of serial transmission are faster and disadvantages of transmission speed. This defect is in front of the new technology that is constantly progressing. No problem.
PCI-E interface of the motherboard
The PCI-E 1.0 standard provides 2.5GT / s (Giga TransmissionPer Second, Giga TransmissionPer Second, Gigaby Transmission / Second, the number of times each second, different from GBPS), and the commonly used PCI-E X16 provides 16-bit data Width, its one-way theoretical bandwidth has been 5Gb / s. Since it is serial transmission, PCI-E 2.0 uses 8bit / 10bit standard. When transmitting data, it will increase the "Start Sign and Termination Sign". The actual transmission of 8bit needs to take up the amount of transfer of 10 bit, so it actually The one-way transmission speed is approximately 4Gb / s. Even so far exceeds the AGP8X 2.1Gb / s. If the two-way data transmission (the rising edge and the falling edge transmits one data), its actual bandwidth can reach 8Gb / s.
The PCI-E 2.0 standard does not modify it, but the transmission speed of 2.5 gt / s is doubled into 5.0 gt / s, in the case of the original constant, the bidirectional bandwidth of PCI-E 2.0 X16 is 16Gb / s. .
At present, the most widely used PCI-E 3.0 standard is upgraded to the transmission speed to 8GT / s, and the transmission standard is upgraded to 128bit / 130bit. The encoding loss can almost ignore, the theoretical bidirection of PCI-E 3.0 x16 can reach 32GB / s.
NVME standard SSD
Recently, the most common NVME protocol has the highest possible-to-state-wide supported bandwidth of 8Gb / s, but the hard disk cannot be read and written at the same time, and the maximum bandwidth can only be one-way 4GB / s, that is, 32GB / s, unit conversion 1byte (byte) = 8bit (bit).
Original link: https://www.eeboard.com/news/ssd-26/
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