Massbus - was: Re: VAX 11/750

Lars Brinkhoff lars at
Fri Feb 26 01:47:27 CST 2021

Rich Alderson wrote:
> As for operating system support, the only DEC operating system which
> could put tapes and disks on the same Massbus was TOPS-20.  Tops-10
> explicitly tells you in the SYSGEN process that disks and tapes must
> reside on different channels; I believe that ITS follows that same
> principle.

KS10 ITS has MIT hacked microcode for IO instuctions hardwired to use
UBA 1 for disk and UBA 3 for tape.

KA10 and KL10 ITS have TM10 I/O bus tape controllers, optionally using a
DF10 channel.

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