CDC 6600 (and 7600)
I just can’t tell you how impressed I was when I first saw the 6600 manual. To begin with it was thin and terse - it was just the most elegant computer that I’d seen, given its incredible speed and inherent complexity. I didn’t begin to understand the complexity or how it really could do.
Everyone’s reaction at looking at the performance numbers was uniformly - “oh my god this thing is fast.” How are they doing all of that? Particularly with a ten megahertz clock but they had four phases - so it was more like a 40 megahertz clock at that time. They were doing floating point operations in 3 cycles - floating point is 300 nanoseconds - so how was he doing it so fast because we were sweating to build an order of magnitude slower unit at the time..