From: Angelo Papenhoff <aap@papnet.eu>
To: tuhs@tuhs.org
Subject: Re: [TUHS] reviving a bit of WWB
Date: Mon, 28 Sep 2020 19:35:56 +0200 [thread overview]
Message-ID: <20200928173555.GA78180@indra.papnet.eu> (raw)
In-Reply-To: <202009251419.08PEJPkV248911@coolidge.cs.dartmouth.edu>
On 25/09/20, Doug McIlroy wrote:
> > Turing save us from 1-complement machines!
>
> Users of Whirlwind II were warned about the quirks of -0.
> We were not warned, though, about integer divide with remainder 0.
> The result of dividing 6 by 3, for example, was binary 1.111111... -
> a valid answer when carried to infinity. Unfortunately, the
> "fractional" part was dropped.
>
> Most people used Whirlwind for floating-point computation, and
> blithely dismissed printed answers like 1.999999 as "roundoff
> errors".
It's funny that you mention that. I'm working on a verilog simulation of
the Whirlwind I right now and I *just* came across this quirk. Now I'm
really glad I remembered this mail of yours. Otherwise I might have
spent some time trying to debug this non-bug. Thanks a lot!
(The simulation is based on the description from 1947, so it doesn't
describe the machine as it actually ran in the 50s. It would be great to
have more material on its later life.)
aap
next prev parent reply other threads:[~2020-09-28 17:42 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-25 14:19 Doug McIlroy
2020-09-28 17:35 ` Angelo Papenhoff [this message]
-- strict thread matches above, loose matches on Subject: below --
2020-09-20 23:00 Norman Wilson
2020-09-20 23:53 ` Clem Cole
2020-09-21 0:00 ` Clem Cole
2020-09-21 2:24 ` John Cowan
2020-09-21 0:09 ` Warner Losh
2020-09-21 1:05 ` Clem Cole
2020-09-21 5:55 ` Steve Nickolas
2020-09-21 5:59 ` Warner Losh
2020-09-21 18:40 ` Paul Winalski
2020-09-21 19:56 ` Dan Cross
2020-09-21 20:50 ` John Cowan
2020-09-21 21:22 ` Rob Pike
2020-09-21 21:57 ` Clem Cole
2020-09-21 23:56 ` John Cowan
2020-09-22 0:54 ` Richard Salz
2020-09-21 21:39 ` Steve Nickolas
2020-09-20 22:51 Norman Wilson
2020-09-19 1:51 Doug McIlroy
2020-09-20 18:42 ` arnold
2020-09-20 19:28 ` Will Senn
2020-09-20 20:12 ` Steve Nickolas
2020-09-20 20:26 ` Doug McIlroy
2020-09-20 20:57 ` Doug McIlroy
2020-09-20 22:13 ` Clem Cole
2020-09-21 20:43 ` Steffen Nurpmeso
2020-09-20 20:58 ` Steve Nickolas
2020-09-20 21:33 ` Brantley Coile
2020-10-07 5:43 ` scj
2020-09-20 21:35 ` John Cowan
2021-02-02 23:08 ` Greg A. Woods
2021-02-02 23:47 ` Larry McVoy
2021-02-03 0:11 ` Dave Horsfall
2021-02-03 0:19 ` Larry McVoy
2021-02-03 2:04 ` Richard Salz
2021-02-03 3:32 ` Dave Horsfall
2021-02-03 4:32 ` M Douglas McIlroy
2021-02-03 11:27 ` Peter Jeremy via TUHS
2021-02-03 20:09 ` Dave Horsfall
2021-02-03 20:13 ` Niklas Karlsson
2021-02-03 23:46 ` Tom Lyon
2021-02-03 22:19 ` Dave Horsfall
2021-02-03 22:55 ` M Douglas McIlroy
2020-09-20 22:15 ` Clem Cole
2020-09-20 22:47 ` John Cowan
2020-09-21 20:48 ` Steffen Nurpmeso
2020-09-21 20:46 ` Steffen Nurpmeso
2020-09-24 2:25 ` Dave Horsfall
2020-09-24 2:33 ` Clem Cole
2020-09-27 5:54 ` Dave Horsfall
2020-09-24 17:19 ` Paul Winalski
2020-09-24 18:17 ` John Cowan
2020-10-07 5:47 ` scj
2020-10-07 9:20 ` arnold
2020-10-08 0:27 ` Dave Horsfall
2020-10-08 3:08 ` John Cowan
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