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From: Michael S <already5chosen@yahoo.com>
Newsgroups: comp.arch
Subject: Re: The Seymour Cray Era of Supercomputers
Date: Mon, 19 May 2025 23:11:22 +0300
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On Mon, 19 May 2025 18:14:17 +0000
mitchalsup@aol.com (MitchAlsup1) wrote:

> On Mon, 19 May 2025 13:35:37 +0000, Michael S wrote:
> 
> > On Sun, 18 May 2025 22:01:19 +0000
> > mitchalsup@aol.com (MitchAlsup1) wrote:
> >  
> >> On Sun, 18 May 2025 8:33:30 +0000, Michael S wrote:
> >>  
> >>> On Sat, 17 May 2025 21:27:04 +0000
> >>> mitchalsup@aol.com (MitchAlsup1) wrote:
> >>>  
> >>>> Did the book relate the story of why CRAY-1 presented a DC-load
> >>>> to the power supply:: that is, the ECL gates were all of the form
> >>>> where they would switch 20 ma into either the true or the
> >>>> complement out- put and thus have no AC energy at the power
> >>>> supply level ??
> >>>>
> >>>> During the CDC 7600 reign, when performing vector calculations,
> >>>> (even though CDC 7600 was not a vector machine, it could stream
> >>>> calculations through its execution window at impressive rates);
> >>>> Certain data bit-patterns in CDC 7600 would cause more Gnd bounce
> >>>> and Vdd drop than the gates cols accommodate and the machine
> >>>> would take a data-dependent hard crash.
> >>>>  
> >>>
> >>> Which voltage, current and frequency are we talking about?  
> >>
> >> Vdd and Gnd which fed the integrated logic gates.
> >>  
> >
> > My question was about absolute numbers. Volts, amperes,
> > nanoseconds.  
> 
> CDC 6600 was built with (effectively) RTL logic using individual parts
> {transistors, resistors, capacitors, ...} well documented in "design
> of a computer" Thornton.
> 
> CDC 7600 was built with some kind of integrated circuits, but not
> TTL or ECL. I don't remember which (its been too long).
> 

I was wondering why the problem was not solved by improvement of
decoupling capacitors.

> >  
> >>>  
> >>>> So, Cray got rid of the problem by presenting a DC-load to the
> >>>> power supply.