Micro Channel architecture (in practice almost always shortened to MCA) was a proprietary 16 or 32-bit parallel computer bus created by IBM in the 1980s for use on their new PS/2 computers. Micro-Channel architecture was designed by IBM engineer Chet Heath and first introduced on the PS/2 series of machines in 1987; it slowly spread to IBM's entire computer line. For a time, MCA could be found in the PS/2, RS/6000, AS/400, and even some of the System/370 mainframes. However, most of these systems later were redesigned to incorporate PCI.