From: "Ronald Natalie" <ron@ronnatalie.com>
To: "Warner Losh" <imp@bsdimp.com>, "Noel Chiappa" <jnc@mercury.lcs.mit.edu>
Cc: The Eunuchs Hysterical Society <tuhs@tuhs.org>
Subject: Re: [TUHS] One's complement (was: reviving a bit of WWB)
Date: Fri, 25 Sep 2020 16:10:23 +0000 [thread overview]
Message-ID: <embf1e21d2-d0d3-459d-ad92-2b67406166ed@alien> (raw)
In-Reply-To: <CANCZdfobDqLuU1dAvmWbhcLXG_u1Eo3WnwZTWFQO201YNiRuHg@mail.gmail.com>
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The DECSystem20 (and the PDP-10 before) were 36 bit two's complement
machines. You had to go back to the PDP-1 if you want one's complement
in the DEC line. The CDCs and UNIVACs were the only ones that were
still kicking around in my era.
>>
>>Just to confirm, I pulled out my PDP-10 Hardware Reference Manual; Vol
>>I - CPU
>>(EK-10/20-HR-001), and it does indeed say (pg. 1-12): "The fixed-point
>>arithmetic instructions use 2's complement representations to do
>>binary
>>arithmetic." Selah.
>
>Back in school, we had our machine organization course. When we learned
>about 1's complement, the professor said "I've used a lot of machines
>that had this. You will likely never see one with it. There are no
>operational machines on campus with that."It stuck with me. We had a
>TOPS-20 machine... the odd turn of phrase was due to a professor that
>had a board of unknown origin hanging on the wall that was a rumored to
>be a CDC or similar... ah, the mid 80s...
Warner
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next prev parent reply other threads:[~2020-09-25 16:17 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-25 15:21 Noel Chiappa
2020-09-25 15:30 ` Warner Losh
2020-09-25 16:10 ` Ronald Natalie [this message]
-- strict thread matches above, loose matches on Subject: below --
2020-09-19 1:51 [TUHS] reviving a bit of WWB Doug McIlroy
2020-09-20 18:42 ` arnold
2020-09-20 19:28 ` Will Senn
2020-09-20 20:12 ` Steve Nickolas
2020-09-24 2:25 ` Dave Horsfall
2020-09-24 2:33 ` Clem Cole
2020-09-25 0:18 ` [TUHS] One's complement (was: reviving a bit of WWB) Greg 'groggy' Lehey
2020-09-25 0:22 ` Warner Losh
2020-09-25 1:39 ` John Cowan
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