outgrowth of : OT: how big would it be? - test-drb@ccmp.vtda.org

20 Oct 1999

So, who makes 256-byte RAM devices at TTL speeds these days.  There are all
sorts of FIFOs of 256 bytes, but I can't find a simple 256-byte RAM any
more.  I also need a 32x8-bit sram, fast (preferably address-access time
<<10ns) and preferably in a small package.

Dick
-----Original Message-----
From: Tony Duell &lt;ard(a)p850ug1.demon.co.uk&gt;
To: Discussion re-collecting of classic computers
&lt;classiccmp(a)u.washington.edu&gt;
Date: Wednesday, October 20, 1999 5:47 PM
Subject: Re: OT: how big would it be?

...

Signetics 82mumble WOM (write only memory) april first version. 
 Oh, she's good.  She's very good. 
 And old...

 Memory says 82s129, I have the data sheet home in that 1971 signetics
 data book.  I was my first ttl databook! 
The 82S129 was a fusible-link PROM. It was an actual device, and in
production until quite recently.

I have here the Signetics data sheet for the 25120 'Fully Encoded 9046*N
Random Access Write Only Memory'. I suspect that's the one you're
thinking of. It includes graphs of 'Bit Capacity .vs. temperature', 'Iff
.vs. Vff', 'Number of pins remaining .vs. Number of socket insertions'
and 'AQL .vs. Selling Price'... :-)

Incidentally the nominal Vff is given as 6.3V. I wonder how many
modern-day engineers would realise the significance.

If anyone wants to get this data sheet, it's reprinted on page 605 of the
'Student Manual for the Art of Electronics' by Thomas C Hayes and Paul
Horowitz (2nd Edition, ISBN 0-521-37709-9)

-tony