DEC Purchase Specifications, particularly 23-000A9-01

[Eric Smith]

On Wed, Jul 17, 2019 at 9:43 AM Mark J. Blair via cctalk <
cctalk at classiccmp.org> wrote:

> > On Jul 17, 2019, at 1:20 AM, Paul Birkel <pbirkel at gmail.com> wrote:
> > From some notes (origin misplaced!) you'll need a typical access time of
> > 40ns from address, or 20ns from /CS:
>
> Thank you! That rules out using a 70ns EEPROM, then.
>

While the bipolar PROMs were faster, I think 70ns will work on an M9312,
though I haven't verified it. The timing for reading the nibbles from the
PROM to assemble into a 16-bit word is controlled by a delay line and
associated logic, and it looks like the required access time is on the
order of 100ns, with a cycle time on the order of 150ns.