I remember the days before putting even a little thing with fins on top of the CPU, much less a fan, or some elaborate liquid cooling loop. They just...sat there on the board, out in the open. Generally, some amount of air would pass by, most of the time. I think my 486 had fins on, like you'd stick on a Raspberry Pi these days.
I also remember applying lots of thermal paste to the heating/cooling block that held the chromatography column in the Beckman 6300 amino acid analyzer. This thing had thermoelectric temperature control to run a temperature gradient on an ion exchange column. It couldn't do a solvent gradient but would step-change between a few different buffers during the run. Detection was post-column ninhydrin and visible light absorbance.
I think the longer column was something like 20 or 30 cm so we're talking a lot of thermal goop compared to a CPU. What a mess! But compared to the mess from getting ninhydrin (conveniently dissolved in, if I remember right, DMSO) all over everything, not so bad, really.
ninhydrin in DMSO. that seems like, if you got it on your skin, it would stain you purple all the way to your bones ~Chara