Multibus

Multibus Description

Multibus I: IEEE-796: Microcomputer System Bus; First released by Intel in 1974. The cards did not use front panels, and they used card edge fingers as the connectors (similar to ISA/PC-AT cards). Companies like Northwest Technical still provide "End of Life" products for Multibus.
However this bus is obsolete and should not be used for new designs.
Some Multibus I cards may still see usage, but they would be over 20 years old at this point.

IEC 796-1:1990 Microprocessor system bus -- 8-bit and 16-bit data (MULTIBUS I) -- Part 1: Functional description with electrical and timing specifications
IEC 796-2:1990 Microprocessor system bus -- 8-bit and 16-bit data (MULTIBUS I) -- Part 2: Mechanical and pin descriptions for the system bus configuration, with edge connectors (direct)
IEC 796-3:1990 Microprocessor system BUS I, 8-bit and 16-bit data (MULTIBUS I) -- Part 3: Mechanical and pin descriptions for the Eurocard configuration with pin and socket (indirect) connectors

The pinouts used on Multibus I seem to be different than those used on Multibus II.
The connectors and board formats are of course completely different, and signal usage.
Note that Multibus II is also listed below, but that bus is obsolete as well.

Multibus II: IEEE-1296 32 Bit Bus, at 80MBps. Card sizes are 3U x 220mm, and 6U x 220mm. These cards are larger then the VME Eurocard sizes which are 3U/6U x 160mm. Uses TTL ('Fast' series) gates for drivers and the Backplane Connectors are DIN41612 type C. Multibus II is not yet considered obsolete, but considered mature; however it is not recommended for new designs. IEEE-STD-1296: High-performance synchronous 32-bit bus: MULTIBUS II, released in 1987, and 1994. Also as ISO/IEC 10861.
ISO/IEC 10861:1994 Information technology -- Microprocessor systems -- High-performance synchronous 32-bit bus: MULTIBUS II

Multibus I, II and III Form Factor

Multibus Board Size and Physical Form Factor

Editor note; most of these pages relating to interface buses carry a list of manufacturers.
But because Multibus is so old, manufacturers are no longer listed.
There is the off chance an OEM still has Multibus cards in stock, but they could be a decade old.
Any Multibus design would have to be re-worked or redesigned because many of the parts might also be obsolete.
So basically it may be cheaper to move to a more up to date interface, but that would be a business decision.

In any event the topic remains to inform new engineers what the Multibus is, so they know not to design to it.
Otherwise some new engineer might try to implement an out of date or obsolete card interface.


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