MBus (SPARC)

The bus permits the integration of several microprocessors on a single motherboard, in a multiprocessing configuration with up to eight CPUs packaged in detachable MBus modules.

Single processor systems were also sold that use the MBus protocol internally, but with the CPUs permanently attached to the motherboard to lower manufacturing costs.

Several related buses were also developed: XBus is a packet-switched bus used in the SPARCserver 1000, SPARCcenter 2000 and Cray CS6400.

This corresponds to the circuit-switched MBus, with identical electrical characteristics and physical form factor but an incompatible signalling protocol.

[1] Manufacturers who produced computer systems using the MBus included Sun, Ross Technology, Hyundai/Axil, Fujitsu, Solbourne Computer, Tatung, GCS, Auspex, ITRI, ICL, Cray, Amdahl, Themis, DTK and Kamstrup.

MBus module, Sun SuperSPARC II SM71
Two MBus connectors (top of photograph), one occupied by CPU module
MBus male connector