-----Original Message-----
From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Mark J.
Blair via cctalk
Sent: Tuesday, July 16, 2019 4:10 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: DEC Purchase Specifications, particularly 23-000A9-01
.....
If 70ns access time parts are sufficient for the M9312's PROMs, then I may
design an emulation with a 5V compatible 28 series EEPROM. If they need to
be faster, then I may need to do something fancier. Or maybe I'll find the
original PROMs that I need and then get distracted and wander off. It may
well be easier to design a replacement for the entire M9312 card than trying
to emulate the individual 512x4 bipolar PROMs, but since when do I do
anything the easy way? I sure wouldn't be playing with 40 year old computers
if I was concerned with practicality and ease of use!
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>From some notes (origin misplaced!) you'll need a typical access time of
40ns from address, or 20ns from /CS:
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DEC boot PROMs on Unibus cards are small bipolar fusible-link PROMs
The A9 types are 82S131 (or MMI6306, 75S171, 27S13, 93448, etc)
16-pin DIL 512-words by 4-bit wide.
Pin spacing is 0.1", pin column pitch is 0.3".
Access times are typically 40ns from address, or 20ns from /CS.
____ ____
| U |
A6 | 1 16 | Vcc
A5 | 2 15 | A7
A4 | 3 14 | A8
A3 | 4 13 | /CS
A0 | 5 12 | D0
A1 | 6 11 | D1
A2 | 7 10 | D2
Vss | 8 9 | D3
|_________|
The F1 types are 82S137 (or TI24S41, MMI6353, 74S573, 27S33, 93453, etc)
18-pin DIL 1024 words x 4-bit wide.
Pin spacing is 0.1", pin column pitch is 0.3".
Access times are typically 40ns from address, or 20ns from /CS.
____ ____
| U |
A6 | 1 18 | Vcc
A5 | 2 17 | A7
A4 | 3 16 | A8
A3 | 4 15 | A9
A0 | 5 14 | D0
A1 | 6 13 | D1
A2 | 7 12 | D2
/CS1 | 8 11 | D3
Vss | 9 10 | /CS2
|_________|
Note for all types: although the types listed are read-compatible,
each brand/type may use a very different programming algorithm.
Also note that these have tri-state outputs; other types (eg 27S13A)
have open-collector outputs.
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And a potentially useful utility from Eric Smith:
https://www.brouhaha.com/~eric/software/m9312/
I have a vague recollection that someone kludged an 11/84 UBA (M8191) in the
manner that you describe but I can't find the reference at the moment.
Perhaps the memory of someone else will be jogged ...
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