A. Internal Connections

Expansion, or add-on, cards use one of three bus types to interface with the computer. The Peripheral Connection Interface (PCI) is the standard expansion card bus used in most computers. The Accelerated Graphics Port (AGP) bus was developed to create a high-speed interface with the CPU that bypassed the PCI bus. This bus was specifically designed for modern video cards, which require a large amount of bandwidth to communicate with the CPU. A newer version of PCI called PCI Express (PCIe) was designed to replace both PCI and AGP as the main bus for expansion cards.

Internal storage devices use one of three separate standards to connect to the bus: parallel AT attachment (PATA), serial AT attachment (SATA), or small computer system interface (SCSI). The term AT refers to the IBM AT computer, first released in 1984. The PATA and SCSI standards were first introduced in 1986; the SATA standard was introduced in 2002 as a replacement for the PATA standard. The SCSI standard is mainly used in servers or high-end systems.