[TUHS] C from 1980 binaries

[Clem Cole via TUHS]

On Wed, Nov 4, 2026 at 9:22 PM segaloco via TUHS <tuhs at tuhs.org> wrote:

>
> All this UNIBUS/QBUS talk has me wondering, what with the clear
> influence of the PDP-11 on the M68000, was there also a line connecting
> VERSAbus and later VMEbus back to the DEC tradition of system buses?
>
As best I can tell, only indirectly.   VERSAbus and VMEbus competed with
Intel's Multibus and Multibus-II.

When Intel originally created Multibus, they were trying to address the
issues with the S-100 bus.   DEC's PDP-8 Ominibus and Unibus had been
around for a long time by then.  I don't think the LSI-11/QBUS was yet
official.  Multibus certainly looked more like the DEC bus offerings than
the S-100 bus, and like DEC when they started, Intel tried to lock them up
the same way DEC had done. By Multibus-II, they certainly succeeded.  But
Multibus, like the S-100 bus and the later PC buses, ended up being 'open.'

For example, the Stanford University Network 68000 board was
Multibus-based, and I don't believe any of their licensees such as VLSI
Systems (ney Sun Micro) needed a license of any type from Intel.  The
Apollo and Masscomp systems also used Multibus as their I/O bus.   But I
know that in the latter case, Masscomp made some extensions on the
undefined connector part of the board edge.   All of their CPUs worked with
COTS Multibus I/O boards, but when Dave Cain created the memory system for
the MC-500, he was fresh off leading both the Comet (750) and the BI
projects at DEC, and Masscomp's memory bus looked more like the BI than
anything else.

FWIW: IIRC, Moto tried to lock up the VMEbus a bit, and I don't know how
well that worked out.  ISTR that Sun switched to it at some point, but
somewhat abandoned it in their own design by the time of the SPARC, although
the larger systems that need more demanding controllers like the ones
Xylogic's built, I think stayed using VME as the I/O bus for a good bit.
Someone like Larry is likely to know much more about that.

Clem