4) PCI-X Bus

The PCI-X interface is an updated version of the connected PCI Bus (peripheral components Interconnect), still using traditional bus technology, but there are more wiring pins, at the same time, all connected devices share all available bandwidths, as described above.

 

1 What is the PCI-X and the original PCI interface is different: a change to the past 32-bit, the PCI-X uses 64-Bit Width to transmit data, so the bandwidth automatically doubled, the length of the expansion slot is inevitably increased. In addition, the other formats, including transmission and communication protocols, signals, and standard connector formats, are compatible, the advantage is that the 3.3 volt 32-bit PCI adapter can be used in the PCI-X expansion slot, of course, if you want, you can also connect the 64-bit PCI-X adapter to the 32-bit PCI expansion slot, however, the bandwidth speed will be greatly reduced. This improved version of bus width doubling applies to specialized storage controllers such as SCSI, iSCSI, fiber channel, 10gbit Ethernet, and InfiniBand, still unable to provide enough bandwidth, So introduce the PCI-SIG (Special Interest Group) interface to provide several different speed levels that can be done from PCI-X 66 (rev. 1.0b) all the way to PCI-X 533 (rev. 2.0) specifications, the following table of these technical details: bus width frequency speed function bandwidth PCI-X 66 64-bit 66 MHz hot ging Ging, 3.3 V 533 MB/spci-x 133 64-bit 133 MHz hot ging Ging, 3.3 V 1.06 GB/spci-x 266 64-bit/16-bit options 133 mhzdouble data rate hot plugging, 3.3 & 1.5 V, ECC supported 2.13 GB/spci-x 533 64/16-bit option 133 mhzquad data rate hot ging Ging, 3.3 & 1.5 V, ECC supported 4.26gb you can see that when the frequency speed reaches 133mhz of PCI-X 133, in order to multiply the bandwidth, the technology of the primary storage and the front-end bus is not enough. Therefore, PCI-X 266 uses double data rate technology, so that every rise and fall of the clock pulse edge can transmit data, so there is a more than doubled the opportunity to transmit data, while the PCI-X 533 specification goes further with the technology that each clock pulse can transmit four times (quad data rate), Intel uses these technologies as early as all Pentium 4 and Xeon processor's front-end bus.

 

2via PCI-X bus structure interpretation when the industry standard ISA and VLB bus has gradually become one of the important reasons to limit system performance, due to ISA (Industry Standard Architecture) the bus can only provide 5-8 Mb/s bandwidth, so the new bus architecture of PCI (Peripheral Component Interconnect) is released. PCI is a 32bit bus architecture that works at 33 MHz, at the same time, the 64bit/66 MHz solution can be provided. For peripherals with high bandwidth requirements, such as SCSI raid, PCI is proposed as a timely rain. Later, PCI began to become the mainstream architecture, but some years later, new problems emerged. When server and high-end PC users find that the 533 Mb/s bandwidth provided by the 64bit/66 MHz PCI bus is still insufficient, a new bus architecture needs to be released in the industry. PCI-X, an extended architecture of the PCI bus, is now known as PCI-X. The 1.0 specification was officially released this year, so some manufacturers began to add support for PCI-X in their design, we are expected to see the PCI-X bus-based products listed around the fourth quarter of this year. But what improvements do PCI-X have in terms of bandwidth compared to PCI 2.2 specifications? Next we will explain in detail PCI-X. Performance unlike the PCI bus, the PCI bus must frequently exchange data between the target device and the bus, while the PCI-X allows the target device to be switched only when a single PCI-X device is viewed as already in progress, if the PCI-X device does not have any data transfer, the bus automatically removes the PCI-X device to reduce the wait cycle between PCI devices. Therefore, at the same frequency, the PCI-X will be able to provide 14-35% higher performance than PCI. [64bit/66 MHz] Another advantage of the bus frequency PCI-X is that it has a scalable frequency, that is, the frequency of the PCI-X will not be as fixed as PCI, however, a device may change as it changes. For example, if a device is working at 66 MHz, it will work at 66 MHz. If the device supports MHz, the PCI-X will work at MHz. PCI-X can support 66,100,133 MHz of these frequencies, and in the future, more frequencies may be supported. [66 MHz PCI-X] A PCI-X controller 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 of the PCI-X, more devices can be supported. The 66 MHz PCI-X has a bandwidth of 533 Mb/s [100 MHz PCI-X] All PCI-X devices work at MHz, at which point the PCI-X bus will manage up to two PCI-X devices, with a 800 Mbit/s bandwidth [133 MHz PCI-X] The most luxurious version of The PCI-X at 64bit bus and MHz frequency, the PCI-X working at 133mhz will be able to provide an astonishing 1066 Mbit/s band width, of course, at this time only one PCI-X device works. However, for some devices that require a lot of bandwidth, such as fiber interfaces, Gigabit Ethernet interfaces, etc., PCI-X 133 will be able to improve many advantages.