[TUHS] A/UX [was Linux is on-topic]

[Warner Losh]

On Fri, Aug 14, 2020, 8:09 PM Dave Horsfall <dave at horsfall.org> wrote:

> On Fri, 14 Aug 2020, Larry McVoy wrote:
>
> > I'm sure everyone here knows this, but the Cray 1 (I think, the one that
> > had what looked like a circular bench seat around the bottom) was
> > designed like that because the clock was at the center and the clock
> > signal went to all the boards and was right because all the clock lines
> > to the boards were the same length.
>
> Yep, timing was everything in those days (and I'm still amazed at the
> people who believe that electricity moves at the speed of light).
>
> Wasn't it Grace Hopper who used to demonstrate a nanosecond by holding up
> a foot of wire?
>

Yes. A nanosecond is just over a foot in copper...  I used to do high
precision timing and we used to make cables specific lengths to bring the
on time point of different parts of the signal distribution system into
alignment... you could also see how bands or kinks in the cables moved the
on time point...

Warner

-- Dave
>
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