It can seem like it is a simpler method of control (why measure temperature if we don't have to?). But they were really very annoying to be around. It wasn't so bad with constant loads, but bursty dynamic loads created an audible cacophony that was very distracting.

Such a system also doesn't necessarily take into consideration other things that affect cooling performance, like ambient temperature and dust.

At least one of the problems (the annoying sounds) can theoretically be worked around by slowing down the rate at which a fan ramps up and down. But by the time that is done, fan speed is back to lagging again -- we're heading back to where we were before.

And then we still have variables like ambient temperature, dust, degraded thermal interfaces, and others to contend with.

So, the simpler method seems to be what we broadly already do today: We change fan speeds based on the temperature of the thing being cooled.

This temperature already has everything we need integrated to begin with: It includes thermal output, ambient temp, dust, old thermal goop, and everything else.

If thing is cool (for whatever reasons it is cool -- maybe it's idling in a shed in January in Minnesota), then: Fan can go slow or even turn off.

If thing is hot (for whatever reasons it is hot -- maybe it's doing real work in a shed in August in Minnesota and full of cat hair), then: Fan can go faster.