RH780 Massbus Adapter

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The RH780 Massbus Adapter was a MASSBUS device controller for the VAX-11/780's Synchronous Backplane Interconnect.

It was implemented on four hex cards, which mount in a custom 6-slot backplane:

Slot Board Acronym Function
1 M8275 MSI SBI/MBA interface
2 M8276 MIR internal registers
3 M8277 MDP MASSBUS data paths
4 M8278 MCP MASSBUS control paths

One slot (5) is unused, and one slot (6) is used (on the back of the backplane) to hold a hex M9041 paddle card, which carries the MASSBUS out on three BC06R flat cables to what appears to be a standard MASSBUS connector, in an 'expansion I/O connector' on the side of the cabinet.

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