William Maddox wmaddox at pacbell.net
Mon Dec 19 00:37:16 CST 2005

William Donzelli wrote:

> The original run of Crays (Cray-1, -1M and 1S) were made from a very small
> number of types. I think the original was made with just four different
> chips in very large numbers: some simple gates, some more simple gates, a
> flipflop, and a memory cell.
> Pretty dumb idea, but Cray often "had to be different". I think the
> original machines could have benefitted by using a wider range of parts
> (like MECL III) - certainly the chip count would have gone way down.

I recall reading that the Cray-1 used balanced logic circuits, in which 
a complementary pair of a signal and its complement were always 
generated, and each fed a terminated transmission line.  The idea was 
that the machine drew essentially constant current regardless of its
logic state.  Perhaps this placed constraints on the chips that could be 
used, as most MSI functions are not implemented in such a perfectly 
symmetric fashion.


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