WITH A PARSIMONIOUS 133 megabytes per second of shared bandwidth, PCI has definitely become the short bus of PC expansion standards. Nearly every other port, slot, and link inside a modern computer is faster than the bus shared by a collection of 32-bit, 33MHz PCI expansion slots and a couple of onboard devices on the typical PC motherboard. A single Serial ATA connection can burst up to 150MB/s, saturating an otherwise-empty PCI bus.

Fortunately, help arrived recently for Pentium 4 motherboards with the introduction of Intel's 915 and 925X chipsets. These chipsets replace the tired PCI bus with the much faster, more modern PCI Express standard. Shared PCI slots give way to PCI Express X1 slots, which offer 250MB/s of dedicated bandwidth in each direction, or 500MB/s total, to a single device. PCI Express also replaces the PCI-derived AGP standard with a new PCI Express X16 slot that offers up to 8GB/s of total bandwidth, or nearly four times the bandwidth AGP 8X.



Link: TechReport