Massbus - was: Re: VAX 11/750

Noel Chiappa jnc at
Wed Feb 24 18:06:12 CST 2021

    > From: Chris Zach

    > technically the MASSBUS cable is just an extension of the Unibus


For one thing, the MASSBUS has no lines for carrying memory addresses. So
there is no way to even build a box that 'translates' MASSBUS to UNIBUS; the
semantics ('the things you can say', basically) of the two busses are so very

(The MASSBUS is actually two separate busses; a control bus, and a data bus.
The former has 5 lines for 'register address', but that's all. While the
control bus is asynchronous, the data bus is synchronous.)


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