I found this IBM heat sink for a 23 die processor interesting.
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> It's Dave, so for those of you that don't like to listen to Dave, I
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Yeah, that's a TCM (Thermal Conduction Module). Back in the late '70s and '80s a lot of IBM's technological lead came from packaging, which allowed them to pack a lot of ECL into a small space, which lets more of the processor be synchronous. ECL's main advantage was its huge transconductance, which lets it drive a lot of capacitance fast.
I remember going to a talk by a mainframe guy who plotted cycle time vs. power dissipation for ECL (IBM ATX-4 process iirc). It rose steeply at very low power due to low transconductance, and more shallowly at high power due to having to space the chips out further for cooling purposes.
Cheers
Phil Hobbs