PCI Express

PCI Express is a new generation bus interface. As early as the spring of 2001, Intel Corporation proposed to use a new generation of technology to replace the PCI bus and the internal connection of multiple chips, and called it the third generation of I/O bus technology. Subsequently, at the end of 2001, more than 20 industry-leading companies including Intel, AMD, DELL, and IBM began drafting specifications for new technologies, which were completed in 2002. They are officially named PCI Express. They use the industry’s current popularity. The point-to-point serial connection, each device has its own dedicated connection than PCI and the earlier shared parallel architecture of the computer bus, does not require bandwidth to the entire bus, and can increase the data transfer rate to a very high Frequency, to achieve the high bandwidth that PCI cannot provide.

PCI Express interfaces vary according to the bus width, including X1, X4, X8, and X16 (X2 mode will be used for internal interfaces instead of slot mode). Shorter PCI Express cards can be inserted into longer PCI Express The PCI Express interface in the slot can support hot swapping, which is also a big leap forward. The PCI Express card supports three voltages of +3.3V, 3.3Vaux, and +12V respectively. PCI Express replaces the AGP interface. With an X16 interface width, it will be able to provide 5GB/s of bandwidth, and even if there is loss in encoding, it can still raise the actual bandwidth of about 4GB/s, far exceeding the bandwidth of 2.1GB/s of AGP 8X.

The PCI Express specification is connected from one channel to 32 channels. It has very strong scalability to meet the different data transmission bandwidth requirements of different system devices. For example, the PCI Express X1 specification supports two-way data transmission with bandwidth per data transmission. 250MB/s, PCI Express X1 has been able to meet the needs of mainstream audio chip, network chip and storage devices for data transmission bandwidth, but far from meeting the graphics chip's demand for data transmission bandwidth. Therefore, PCI Express X16 must be used, ie 16 The point-to-point data transmission channel is connected to replace the traditional AGP bus. The PCI Express X16 also supports bidirectional data transmission. The data transmission bandwidth per direction is up to 4 GB/s, and the bidirectional data transmission bandwidth is as much as 8 GB/s, compared to the current wide range. The AGP 8X data transmission used only provides 2.1GB/s data transmission bandwidth.

Although the PCI Express specification allows X1 (250MB/sec), X2, X4, X8, X12, X16, and X32 channel specifications, PCI Express X1 and PCI Express X16 will be the mainstream PCI Express specification, as currently seen. Chipset vendors will add support for PCI Express X1 to Southbridge chips, and add PCI Express X16 support to Northbridge chips. In addition to providing extremely high data transfer bandwidth, PCI Express uses serial packet data transfer methods. Therefore, each pin of PCI Express interface can obtain more bandwidth than the traditional I/O standard, which can reduce the cost and volume of PCI Express equipment. In addition, PCI Express also supports high-level power management, hot swap support, and support. Data synchronization transmission, bandwidth optimization for data transmission priority.

In terms of compatibility, PCI Express is compatible with current PCI technologies and devices at the software level and supports the initialization of PCI devices and memory modules. That is to say, the current driver allows the operating system to support PCI Express devices without requiring a resumption. .PCI Express is a new generation of next-generation architecture that can provide a lot of bandwidth and rich functionality to enable exciting new graphics applications. PCI Express can allocate bandwidth for bandwidth-hungry applications, greatly improving CPU and graphics processing. The bandwidth between devices (GPUs). For the end user, they can experience cinematic image effects and get a seamless multimedia experience.

PCI Express transmits data in a serial manner. It is different from the original ISA, PCI, and AGP buses. This transmission method does not have to affect the performance of the entire system due to the frequency of a certain hardware. Of course, the entire system is still As a whole, but we can easily increase the frequency of a low-frequency hardware, so that the system can be used without a bottleneck environment. In order to enhance the efficiency of frequency enhancement in a serial manner, the key constraint is what kind of physical transmission medium. Copper wires are commonly used, and theoretically the copper material can provide a transmission limit of 10 Gbps. This is why PCI Express's limit transmission speed answers.

Because the PCI Express mode of operation is a method called “differential voltage transfer.” Two copper lines represent the logic symbols 0 and 1 by the voltage difference between each Other. Data transmission in this way can support the poles. High operating frequency. So after the speed reaches 10Gbps, the performance can be doubled by simply replacing the fiber (Fibre Channel).

PCI Express is the next phase of the main transmission bus bandwidth technology. However, the GPU's demand for bus bandwidth is the highest among subsystems. Obviously, video should have a certain weight in PCI Express. Obviously, the PCI Express proposal is not It is an end to the bus format. On the contrary, the maturity of its technology still needs this time. Of course, at this time, whether those chips, motherboards, video and other manufacturers can come out to support is the key to the development of PCI Express. However, it is still being Although the gap between the performance of the promising AGP8X and the performance of PCI Express is not obvious, the gap will be self-evident as PCI Express improves.

PCI-Express is the latest bus and interface standard. Its original name was "3GIO," which was proposed by Intel. It is clear that Intel means that it represents the next-generation I/O interface standard. Passed by the PCI-SIG (PCI). After the certification, the special interest organization was renamed "PCI-Express". This new standard will fully replace the current PCI and AGP, and ultimately achieve the unification of the bus standard. Its main advantage is the high data transfer rate, currently up to 10GB. /s and above, but there is still considerable potential for development. PCI Express also has a variety of specifications, from PCI Express 1X to PCI Express 16X, to meet the current and future demand for low-speed devices and high-speed devices within a certain period of time. Can support PCI Express is mainly Intel's i915 and i925 chipset. Of course, to achieve a full replacement of PCI and AGP also takes a long process, just as PCI replaced ISA, there will be a transition process.