From: Warner Losh <imp@bsdimp.com>
To: 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 09:30:46 -0600 [thread overview]
Message-ID: <CANCZdfobDqLuU1dAvmWbhcLXG_u1Eo3WnwZTWFQO201YNiRuHg@mail.gmail.com> (raw)
In-Reply-To: <20200925152108.2AD1218C0C1@mercury.lcs.mit.edu>
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On Fri, Sep 25, 2020, 9:22 AM Noel Chiappa <jnc@mercury.lcs.mit.edu> wrote:
> > From: Warner Losh
>
> > I'm pretty sure PDP-10 wasn't 1's compliment / was 2's compliment..
>
> 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 15:31 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 [this message]
2020-09-25 16:10 ` Ronald Natalie
-- 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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