The electronics dictated the shape. Each wire of the backplane had to be made to exact and precise length because the ECL (emitter-coupled-logic) was very, very fast in its day. It was also power-hungry, incredibly electrically noisy and hard to get working reliably.
As I recall, there were exactly four (4) different types of small-medium scale logic circuits in the CPU.
I casually interviewed for field engineering there early in one of my careers but they wouldn’t even look at you if you didn’t have 10 years of experience. And you had to have an unusual skillset - high-speed logic diagnostics AND HVAC (refrigeration was built-into the computer).
You could make a case that what Wozniak did with finesse and as little money and chips as possible, Cray went the other way - that machine really was a “money was no object” computer.
Yep. Years ago I designed a few products with ECL -- wonderful non-saturating/linear differential logic -- and had the "luxury" of using chips with one flip-flop per IC so I didn't have to build up the flops from gates.
The noise wasn't so much the logic gates themselves as it was the power busses and the 50-ohm termination supply. It took an outrageous amount of supply bypass capacitance, carefully distributed, to keep the thing stable.
But once you had it, it ran beautifully. I was never disappointed by my ECL circuits. Hell to build, but man they ran great.