PCI-Express

PCI-Express (formerly known as 3GIO for 3rd Generation I/O) is a new implementation of the PCI computer bus that uses existing PCI programming concepts and communications standards, but bases it on a much faster serial communications system. It is being supported primarily by Intel, who started working on the standard as the Arapahoe project after pulling out of the InfiniBand system. PCI-Express is intended to be used as a local bus only. Due to it being based on the existing PCI system, cards and systems can be converted to PCI-Express by changing the physical layer only – existing systems could be re-booted on PCI-Express and never even know it. The higher speeds on PCI-Express allow it to replace almost all existing internal buses, including AGP and PCI, and Intel envisions a single PCI-Express controller talking to all external devices, as opposed to the current northbridge/southbridge solution in current machines. PCI-Express is not, however, fast enough to be used as a memory bus. In this respect it is at a distinct disadvantage to the similar HyperTransport which can be used for this role as well. In addition PCI-Express does not offer the flexibility of the InfiniBand system, which has similar performance, but can be used for both internal and external buses. PCI-Express appears, at the time of writing in 2004, to be well on its way to becoming the new backplane standard in PC's. High-end graphics cards from both ATI Technologies and nVidia have recently been converted from AGP to PCI-Express, which may be the incentive needed for other companies and devices to follow suit. \n

External links

\n:Creating a Third Generation I/O Interconnect (PDF)\n:Intel Developer Network for PCI Express Architecture \n