DEC Purchase Specifications, particularly 23-000A9-01

Eric Smith spacewar at
Wed Jul 17 17:56:59 CDT 2019

On Wed, Jul 17, 2019 at 4:31 PM Bob Smith <bobsmithofd at> wrote:

> Listed as a 50NS part
> 27S32 is listed at 70NS part.

70ns is the mil temp range rating for the 27S32; the commercial spec is 55
70ns parts would probably work fine in an M9312, as would any bipolar PROM
with the same memory organization and pinout.

I expect that 70ns doesn't meed the DEC purchase specification for
23-000A9-01, but unless we turn up a copy of the actual purchase
specification, we won't really know. It seems likely that the purchase
specification would have required 55ns, as that was a very common "slow"
speed grade for bipolar PROMs. Almost all bipolar PROM vendors offered at
least one faster speed grade, but they cost more so DEC would only have
specified that for designs that needed it, and it would have had a
different purchase specification, rather than the common 23-000A9-01.

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