discrete transistors

From: William Donzelli <william_at_ans.net>
Date: Wed Oct 21 08:51:20 1998

> Although I never looked at the prints for one, all of the Cray 1's that I
> had a chance to examine were not completely circular--there was always a
> wedge missing.

The small X/MPs typically used only about a third of the circle. The
advantage to the form probably did not matter with such a small system,
but it did keep the factory floor standard. The design persisted until the
Y/MP (first style), where they went with the rude shape (well...look at it
from above).

When a tradional Cray had an SSD attached to it (essentially a boatload of
secondary memory), the circle completed. The SSD, taking up the missing
quarter of the circle, sat just a few feet out, connected by a big tube
for the wires.

> I suspect that the reason Seymour Cray built the machine in the shape he
> did was that the circuit cards, plus the machined columns that supported
> and cooled them, were wider than the card connectors. By arranging the
> card columns in a semi-circle with the connectors on the inside, he could
> minimize wiring length.

Very true.

William Donzelli
william_at_ans.net
Received on Wed Oct 21 1998 - 08:51:20 BST