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From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.arch
Subject: Re: Why VAX Was the Ultimate CISC and Not RISC
Date: Sat, 08 Mar 2025 10:52:36 GMT
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
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EricP <ThatWouldBeTelling@thevillage.com> writes:
>Looking at the Signetics 82S100 in 1976 has max access of 50 ns, 600 mw
>in a 28 pins dip.

The Commodore 64 used a 82S100 or compatible for various purposes,
especially for producing various chip select and RAM control signals
from the addresses produced by the CPU or the VIC (graphics chip).
Thomas Giesel wrote a very detailed report
<http://skoe.de/docs/c64-dissected/pla/c64_pla_dissected_a4ds.pdf> on
the original PLAs and their behaviour, in order to replace it
(apparently it's a chip that was failure-prone).


He reports that the 82S100 generates the #CASRAM signal with a
propagation delay of 35ns in one direction and 25ns in the other, and
the #ROMH signal with a propagation delay of 25ns in both directions
(table 3.4).  I guess that the 50ns are the worst case of anything you
can do with the 82S100.

He reports a current consumption of 102mA for the 82S100 (table 3.3),
which at 5V (the regular voltage at the time) is pretty close to the
600mW given in the data sheet.  The rest of the board, including
several chips with much more logic (CPU, VIC, SID (sound), 2xCIA
(I/O)) , consumed at most 770mA in his measurements; most of the rest
was NMOS, while the 82S100 was TTL.

- anton
-- 
'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'
  Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>