A desktop computer's interior components can be added using the PCI hardware interface. A PCI card, for instance, can be placed into a PCI space on a processor to add more I/O connections to a computer's rear.

Intel created the PCI architecture, also referred to as "standard PCI," which was unveiled in 1992. From the early 1990s to the middle of the 2000s, a lot of desktop Computers had slots for two to five PCI devices. Each card needed a free space on the processor as well as a detachable panel on the system unit's rear. Since you could add a speedier cable or wireless network, a better video card, or new interfaces, like USB 2.0, to PCI devices, upgrading a computer was simple.

Data transmission speeds of 133 gigabytes per second were enabled by the initial 32-bit, 33 MHz PCI specification. A few years later, an improved 64-bit, 66 MHz standard was developed, enabling much higher data transmission speeds of up to 533 MHz. Backward-compatible PCI-X (also known as "PCI eXtended") was launched by IBM, HP, and Compaq in 1998. Up to 1064 MHz of data transmission speeds were enabled by the 133 MHz PCI-X link.

When PCI Express was released in 2004, it replaced both PCI and PCI-X.