Abstract: A high performance terminal input/output subsystem for connecting a multiplicity of user devices to a multi-user computer includes a single-board host adapter which is mounted in a single bus slot in the host computer card cage and provides the communication between the subsystem and the host computer. One or more multiple terminal, intelligent cluster controllers is remotely located from and coupled to the host adapter by means of a coaxial cable. The cluster controllers are multidropped from the coaxial cable in daisy chain fashion. Communication between the host adapter and cluster controllers utilizes a high speed communication line employing a 2.5 Mbit/second baseband, token-passing, serial bus, local area network protocol. Each cluster controller provides local terminal connections for 8 or 16 user devices.