MCA
Short for Micro Channel Architecture, MCA was introduced by IBM in 1987 as a competitor to the ISA bus. The MCA bus offered several additional features over the ISA such as a 32-bit bus (although there was also a 16-bit bus), ran at 10MHz, automatically configure cards (similar to what Plug and Play is today), and bus mastering for greater efficiency. The primary downfall of the MCA bus was that it was a proprietary bus and required licensing fees. Because of its proprietary format and competing standards the MCA bus never became widely used and has been fazed out of the desktop computers. Below is an example of a MCA network card and what a MCA card may look like.
Also see: Bus, EISA, ISA, Motherboard definitions