As PCI Slots has grown to become the default expansion technology for industrial applications, so have the variety of available PCI Slot technologies. It's easy to be confused by the number standards. Let's look at each and see what they do. The best industrial computers offer a combination of these expansion slots to accommodate a variety of devices.
1. 3.3V/5V 32-Bit PCI Slot -PCI remains an accepted standard despite several newer revisions. A regular PCI uses five volts of power. You can differentiate it from the rare 3.3-volt type by the position of the notch in the slot. If the notch is toward the edge of the motherboard, the slot is 5 volts. If the notch is toward the center of the motherboard, it's 3.3 volts. The differing voltages correlate to different notches on the device card.
2. 3.3/5V 64-Bit PCI Slot -An extended connector can allow the device bus to double its speed of data transfer. 3.3V/5V 64 bit slot is longer to accommodate the additional connectors required.
3. PCI-X - PCI-X is a double-wide PCI device slot and runs at 4x the speed. It enhanced the 32-bit PCI Local Bus for higher bandwidth demands for servers. It has itself been replaced in modern designs by PCI Express.
4. PCIe PCI Express is used in consumer, server, and industrial applications, as a motherboard-level interconnect (to link motherboard-mounted peripherals) and as an expansion card interface for add-in boards. PCIe is based on point-to-point serial links, rather than a shared parallel bus architecture, like standard PCI. PCIe x1, PCIe x4, PCIe x16 are different slot sizes in the PCIe standard.
Whether you need 32-bit PCI Slots or one of the other useful types, the standard is here to stay. They are becoming increasingly hard to find in new systems and require specific engineering to meet your device needs.

Article Source: http://EzineArticles.com/?expert=Josh_Gwinn