The terms Micro Channel, Micro Channel architecture, or just MCA, all refer to the same thing: a kind of expansion bus used in PCs. MCA was a distinct break from previous bus architectures such as Industry Standard Architecture. The pin connections in MCA are smaller than other bus interfaces. For this and other reasons, MCA does not support other bus architectures. Although MCA offers a number of improvements over other bus architectures, its proprietary, nonstandard aspects did not encourage other manufacturers to adopt it.