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From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: one's complement (was: NULL, zero, and readable code)
Message-ID: <6106@brl-smoke.ARPA>
Date: Sun, 12-Jul-87 16:17:44 EDT
Article-I.D.: brl-smok.6106
Posted: Sun Jul 12 16:17:44 1987
Date-Received: Mon, 13-Jul-87 04:49:54 EDT
References: <8170@brl-adm.ARPA> <13222@topaz.rutgers.edu> <6090@brl-smoke.ARPA> <266@swlabs.UUCP> <1807@megaron.arizona.edu>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) )
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 13

In article <1807@megaron.arizona.edu> gmt@arizona.edu (Gregg Townsend) writes:
>....  I assume this was just conceptual
>and actually involved negative logic instead of extra gates.

Correct; since CDC used a form of (unsaturated) RTL, each gate acted as an
inverter modified by a second signal (the gate signal).  Their circuit
diagrams were pretty cute: squares and circles alternated as the signal
switched from positive to negative logic on its path through the transistors.

The reason for this architecture was speed via both fast (unsaturated)
switching logic and minimal gate count (therefore no extra inverters
just to make the logic diagrams more intelligible).  After one got used
to it, it all made perfect sense.