PCI Extended Vs PCIe - Difference Between PCI-X and PCI Express
It is important to understand differences between the PC expansion bus technologies, especially when purchasing multi-port serial cards, Ethernet controllers, or video cards. PCI Extended (PCI-X) and PCI Express (PCI-E, PCIe) are two technologies in particular with similar names that often get confused with each other.
PCI stands for Peripheral Component Interconnect, and was developed by Intel in 1993. As speeds and performance of personal computers have increased, so has the need for new PCI connection options; PCI Extended and PCI Express are two resulting iterations. They are both high-speed PC expansion interface buses for internal peripherals, but are very different technologies.
PCI-X stands for Peripheral Component Interconnect Extended - a technology developed in 1998 by IBM, HP and Compaq. PCI-X took the PCI standard and doubled the clock speeds from 66Mhz to 133Mhz. PCI-X was designed so all older PCI cards would fit and work in the PCI-X slots that the PC manufactures were shipping, thus saving consumers from having to buy new PCI-X specific cards.
PCIe was created in 2004 by Intel as a replacement for the PCI architecture they designed in 1993. PCI Express is a new PC expansion interface connection that doesn't offer any backward compatibility to legacy PCI cards. Other than the actual connection itself, the technology variation is the biggest differentiator. A PCI Express connection is based on point-to-point connections or "lanes." PCI and PCI-X technology use a bus-based system that shares a 32- bit signal path.
When purchasing a server or a PC, remember to note what slots (PCIe, PCI-X, etc.) are available on the motherboard when shipped. Chances are the slots will be either a singular technology or combination of two current expansion interfaces.
Rob Iten is director of vertical markets and channel sale at Comtrol Corporation, manufacturer of Ethernet device servers and multi-port serial cards Over the past 25 years, Comtrol has evolved its PC expansion bus technologies with PCI-X and PCIe technologies.
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