How were 32-bit minis built in the 70s/80?

Ethan Dicks ethan.dicks at
Mon May 13 10:31:02 CDT 2019

On Mon, May 13, 2019 at 8:20 AM Paul Koning via cctalk
<cctalk at> wrote:
> > There were also the AMD2901, 2903, 29203 family of bit-slice components, with the 2910 sequencer.
> The VAX 730 was built with 2901s.

Yep.  I pulled some 2901s from a VAX 11/730 CPU board in the early 90s
to repair a Tempest "Math Box" (we were doing our own repairs on our
VAXen in the late 80s/early 90s, and we had a stack of dead and
questionable boards in our engineering area, so one gave its life to
repair an arcade machine).

> On the subject of custom chips:  DEC used gate arrays a lot.  For example there is the Pro 380 in which much of the discrete chip logic from the Pro 350 has been absorbed into one or two gate arrays, with all the unnecessary flexibility of the original chips omitted.

What sort of flexibility was omitted?  I have both models and the
board layout difference is obvious (there's so much room on the Pro380
that it has a huge RAM field right on the mainboard instead of on two
daughter cards (plus any on the CTI bus).


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