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Re: old architectures, was Accumulator naming

From John Levine <johnl@taugh.com>
Newsgroups alt.sys.pdp10
Subject Re: old architectures, was Accumulator naming
Date 2026-07-30 20:40 +0000
Organization Taughannock Networks
Message-ID <114gcrj$19ct$1@gal.iecc.com> (permalink)
References <87wlulwflh.fsf@atr2.ath.cx> <87se579i01.fsf@atr2.ath.cx> <mddqzklxxa5.fsf_-_@panix5.panix.com> <yTJaS.915$bZ8b.769@fx01.iad>

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According to Scott Lurndal <slp53@pacbell.net>:
>The 8080 architecture has been obsolete for quite some time;  if you're
>looking for architectures contemporaneous with the PDP-6/10/DS20, perhaps
>the Burroughs medium systems would be a better comparison.

A reasonable choice but I think the Univac 1100 and GE 635 are better peers,
being late 36 bit word addressed architectures sort of resembling the IBM 709x,
and also S/360 which is the only peer I know with 16 uniform registers.

The 635 was single accumulator with 7 index registers like the 7094.  It had very
complicated addressing modes you can read about on Wikipedia.

The Unvac 1100 had 15 index registers and 16 accumulators mapped into low memory
sort of like the -6, except for some reason the index regs were octal 001 to 017
while accumulators were 014 to 033, with ac's 0 to 3 aliased to index 12 to 15.

S/360 had (still has in zSeries) 16 registers of which all but R0 can be used as index
or base registers.  Unlike the -6 or 1100, the registers are separate from memory.  It
has LM and STM instructions to load or store a range of registers, usually used in
function call prolog and epilog.

But anyway, there's nothing odd about registers having numbers.  The x86 scheme where
each register is named and special is quite peculiar but we're used to it because x86
has become so popular.
-- 
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly

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Thread

Fizz Buzz jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-07-23 17:39 -0400
  Re: Fizz Buzz Rich Alderson <news@alderson.users.panix.com> - 2026-07-23 23:19 -0400
    Re: Fizz Buzz jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-07-25 12:00 -0400
      Re: Fizz Buzz Rich Alderson <news@alderson.users.panix.com> - 2026-07-25 18:05 -0400
        Re: Fizz Buzz jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-07-26 11:12 -0400
      Accumulator naming Rich Alderson <news@alderson.users.panix.com> - 2026-07-29 18:10 -0400
        Re: Accumulator naming scott@slp53.sl.home (Scott Lurndal) - 2026-07-30 15:14 +0000
          Re: old architectures, was Accumulator naming John Levine <johnl@taugh.com> - 2026-07-30 20:40 +0000
          Re: Accumulator naming Rich Alderson <news@alderson.users.panix.com> - 2026-07-30 18:41 -0400
        Re: Accumulator naming jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-07-30 11:24 -0400
          Re: Accumulator naming scott@slp53.sl.home (Scott Lurndal) - 2026-07-30 16:03 +0000
          Re: Accumulator naming Rich Alderson <news@alderson.users.panix.com> - 2026-07-30 18:56 -0400
            Re: Accumulator naming cross@spitfire.i.gajendra.net (Dan Cross) - 2026-07-30 23:48 +0000
              Re: Accumulator naming John Levine <johnl@taugh.com> - 2026-07-31 01:31 +0000
                Re: Accumulator naming cross@spitfire.i.gajendra.net (Dan Cross) - 2026-07-31 02:52 +0000
                Re: Accumulator naming John Levine <johnl@taugh.com> - 2026-07-31 03:36 +0000
                Re: Accumulator naming Lars Brinkhoff <lars.spam@nocrew.org> - 2026-07-31 13:40 +0000
          Re: Accumulator naming Lars Brinkhoff <lars.spam@nocrew.org> - 2026-07-31 13:35 +0000
          the Ten Heavenly Stems (was Re: Accumulator naming) Kragen Javier Sitaker <kragen@canonical.org> - 2026-09-11 16:07 -0300
            Re: the Ten Heavenly Stems (was Re: Accumulator naming) Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-09-14 01:12 +0800
              Re: the Ten Heavenly Stems (was Re: Accumulator naming) Kragen Javier Sitaker <kragen@canonical.org> - 2026-09-14 14:40 -0300
                Re: the Ten Heavenly Stems (was Re: Accumulator naming) scott@slp53.sl.home (Scott Lurndal) - 2026-09-14 18:09 +0000
                Re: the Ten Heavenly Stems (was Re: Accumulator naming) quadibloc@invalid.com (John Savard) - 2026-10-26 03:00 +0000
  Re: Fizz Buzz "Kerr-Mudd, John" <admin@127.0.0.1> - 2026-08-21 13:27 +0100

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