Short for Micro Channel Architecture, MCA was introduced by IBM in 1987 as a competitor to the ISA bus. MCA offered several additional features over the ISA such as a 32-bit bus in addition to the standard 16-bit bus). Also, it automatically configured cards (similar to what plug and play is today), and included bus mastering for greater efficiency.
The primary downfall of the MCA bus was that it was proprietary and required licensing fees. Due to this format and competing standards the MCA bus never became widely used and was phased out of the desktop computers in the mid-1990s. The MCA bus was superseded by the ISA bus, which was later replaced by PCI.