Differences between PCI, PCI-X, and PCI-E

Differences between PCI, PCI-X, and PCI-E
I. PCI Bus
The PCI bus standard was developed by PCISIG in 1992 and has a history of more than eight years. Total PCI bandwidth = 33MHz × 32BIT/8 = 133 MB/S.
2. PCI-X Bus
The PCI-X increases the total PCI bandwidth from 133 MB/s to 1.066 GB/s based on PCI V2.2, which adds power management and hot swapping technology. At the same time, it also adopts a multi-task design that allows a device that is requesting data from a target device to handle anything else before the target device is ready; in the current PCI system, the device does not care about anything before completing a request. At this time, the bus clock cycle is wasted. At the same time, the PCI-X also allows devices that are not ready to send data to be removed from the bus, so that the bus bandwidth can be used by other transactions, greatly increasing the utilization of the bus. So, at the same frequency, the PCI-X will be able to provide 14% ~ higher than PCI ~ 35% performance. The PCI-X also uses the same-bit standard size data block design with the IA-64, so that the data block size through the bus is the same, this provides more pipeline mechanism, improves processor management.

PCI-X is currently divided into 66 MHz, MHz and 133MHz three versions. PCI-X controllers working at 66MHz will be able to access up to 4 PCI-X devices, of course, if a PCI-X is added to a bridge chip for the PCI-X, more devices can be supported. The 66 MHz PCI-X has a bandwidth of 533 Mb/s. The PCI-X bus is shared and has three types: 66,100 and 133.

100 MHz PCI-X devices are working at 800 MHz, at which point the PCI-X bus can only manage up to two PCI-X devices, at 64 bit bus and MHz frequency, with Mbit/s of bandwidth.

The most luxurious 133 MHz PCI-X operates at 133 MHz and will be able to deliver an astonishing 1066 Mbit/s band width.

3. PCI-E Bus
PCI Express is a new generation of graphic architecture that provides a large amount of bandwidth and rich features. PCI Express can greatly increase the bandwidth between the central processor (CPU) and the graphics processor (GPU. For end users, they can experience cinema-level image effects and achieve a seamless multimedia experience.

Pci-x is not independent. According to the development of PCI bus, pci-pcix-pcie is designed to improve the transmission speed of PCI. Pci is 32-bit 33 mhz, pcix is 64-bit to provide a maximum of 13 3 mhz frequency, pcie is able to provide a higher speed in the current frequency through the serial mode multi-channel combination, all interfaces in the future will be PCIE, not just graphics cards.

PCI-E bus is a new bus specification completely different from the past PCI bus, compared with the PCI bus shared parallel architecture, PCI Express bus is a point-to-point serial connection device connection method. Point-to-point means that each PCI Express device has its own independent data connection, and the concurrent data transmission between devices does not affect each other, in the past, there was only one device on the PCI bus for communication. Once the number of connected devices on the PCI bus increased, the actual transmission rate of each device would decrease, performance is not guaranteed. Currently, PCI Express processes communication in a point-to-point manner. Each device establishes its own transmission channel when requesting data transmission. This channel is closed for other devices, this operation ensures channel uniqueness and avoids interference from other devices.

PCI-X is an extended architecture of the PCI bus, the PCI-X frequency is not as fixed as PCI, but can change with the change of equipment. The PCI-X uses a 64-bit PCI bus that supports 66,100,133 MHz of these frequencies. In the future, more frequency support may be provided. The PCI-X standard is mainly oriented to the server I/O structure. The PCI-X is designed to increase the transmission speed between the CPU and peripherals, and increase the I/O speed of the server by twice. Different from the original PCI standard developer, the sequent of PCI was jointly developed by IBM and other computer manufacturers.

PCI-X such a port on the general PC motherboard can not see, most are on the server motherboard. This slot seems to be PCI reinforced, the slot is very long, it supports both PCI-X and PCI plug-in card.

PCI-Express (PCI-E) is the latest bus and interface standard, its original name "3GIO", was proposed by Intel. Intel stands for the next generation of I/O interface standards. Changed to "PCI-Express" only after being certified by the PCI-SIG (PCI special interest organization ". This new standard will completely replace the current PCI and AGP, and ultimately implement the unification of bus standards. Its main advantage is its high data transmission rate, which can reach a maximum of 10 Gb/s.
PCI Express bandwidth (two-way transmission mode ):
1 lane-x1: 500 MB/s
4 lane-x4: 2 GB/s (2000 MB/s)
8 lane-x8: 4 GB/s (4000 MB/s)
16 lane-x16: 8 GB/s (8000 MB/s)
X16 is the most common among them. It basically replaces the AGP slot and becomes the interface standard of the video card. It can provide 5 Gbit/s bandwidth, while the AGE 8X bandwidth is 2.1 GB/s.

The X2 mode is used for internal interfaces instead of slots. The PCI-E specification is connected from one channel to 32 channel connections, with very strong scalability to meet different system equipment for different data transmission bandwidth needs. In addition, short PCI-E cards can be inserted into longer PCI-E slots for use, PCI-E interfaces can also support hot plugging.

The PCI-X was proposed by IBM, HP, And Compaq, which is a parallel interface and PCI-compatible correction.
PCI-E, also known as PCI-Express and PCIe, is proposed by Intel, which is a serial interface and is not compatible with PCI.
The trend now is that PCI-E will replace PCI and PCI-X as well as AGP, just as in the year when PCI replaced ISA.

You can also use this method to calculate the bandwidth of a bus that has a great relationship with the memory bandwidth, such as PCI and AGP. For example, the PCI bandwidth = 33MHz × 32BIT/8 = 133 MB/S, and the bandwidth of the AGP 1X bus is 66MHz × 64BIT/8 = 528 MB/S, AGP 4X bandwidth = 528MHz × 4 = 2.1 GB/second.

 

From: http://netnewsme.blogspot.com/2009/03/pcipci-xpci-e.html