Take overclocking. You have a processor, and if you tell it to run at 1.5x the given clock speed, you get 1.5 the performance. And a gob of heat. Which you then get a better heat sink to take care of.
Let's consider the opposite. You're there, you're doing work, but your workspace is too frakin' hot! What's your alternative? Underclocking. But don't you have to poke at the BIOS for that? Maybe mobo jumpers? Certainly reboot?
PC World has an article on a software tool to handle just that situation, turning down the CPU speed when the server room heat becomes too much. (Yeah, it's a server thing. It isn't something that makes too much sense unless you have huge rooms full of servers, each full of long-running jobs.)
And I was in a Linux User Group with both guys in the article. So cool.