It is an extension connector developed by IBM and used in the PS/2 desktop computers manufactured by the firm. The amount of I/O interfaces can be increased by adding more devices by connecting them to the hardware of the computer via an extension bus. In addition to many others, these include SCSI, USB, Firewire, AGP, and HDMI interfaces.

The AT and ISA networks used in earlier IBM PC/AT equivalent systems were intended to be replaced by the MCA specification. Even though the MCA bus design outperformed AT and ISA in terms of capacity and performance, IBM retained it as a private standard. Due to the MCA architecture's incompatibility with other standards, this deterred other makers from implementing the standard. The majority of PC manufacturers included the more commonly used PCI and AGP extension ports in their machines.