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From: John Ames <commodorejohn@gmail.com>
Newsgroups: comp.os.linux.misc,alt.folklore.computers
Subject: Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth
Date: Mon, 21 Jul 2025 09:32:37 -0700
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On Sat, 19 Jul 2025 07:14:12 -0000 (UTC)
Lawrence D'Oliveiro <ldo@nz.invalid> wrote:

> > For sure it's a really limited Unix port since the target HW is the
> > original PC or PC/XT.  
> 
> Which is still way more powerful than an early-1970s-vintage PDP-11,
> which is what Bell Labs Unix was originally developed on, and for.

Hmm, that's an interesting question, actually - the Bell Labs -11 was
an 11/45, which was much faster than the original -11s, while the IBM
PC was really a bit of a dog thanks to having a 16-bit architecture on
an 8-bit bus and the generally poor performance characteristics of the
first-generation x86 CPUs. It'd be neat to do a head-to-head shootout.
I don't know if it's recorded whether the Bell Labs -11 was core or
semiconductor memory (980 vs. 450 ns cycle time;) the PC at 4.77 MHz
would have a cycle time of around 209 ns, but with the aforementioned
8-bit bus. As a naive approximation, that might put them anywhere from
comparable to around twice the memory bandwidth for the PC...but then
the 8088's instruction times are kinda abysmal even on top of that.
Definitely makes one curious...