[dhosek]

The supercomputers (all?) used wirewrap rather than PCBs. I heard a story once about someone coming in for a demo of a supercomputer and Cray realized there was a bug in the hardware during the demo and while the potential customers were at lunch, he rewired the machine to fix the bug.

[Animats]

Right. Seymour Cray said that the two big problems in supercomputing were "the thickness of the mat" (of wires on the backplane) and getting rid of the heat.

This is a Cray-I backplane.[1]

[1] https://www.flickr.com/photos/geekmuseum/2926520634/

[syockit]

I wonder if any of his machines ever caught fire, causing an localized out-of-season aurora borealis. On the other hand, Cray machines are never mentioned in the "Halt and Catch Fire" machine code instruction humor.