Computer gets abnormally hot when running Doom

[randi]

Isn't the FPS capped to 200 by default?

Yes, vid_maxfps defaults to 200, but you can set it to 0 if you want to go full throttle.

[Marisa the Magician]

I still remember the fancy tearing side effect of having uncapped fps and using A_Quake. The screen just ripples horizontally.

[Graf Zahl]

but this is a 23-year old game.

... but it's not a 23 year old engine. I don't understand why people still fall into this logic trap.
The 23 year old game ran at 35 fps with 320x200 pixels, it had no concept of what modern hardware can do - and if you run that 23 year old engine today you indeed wont see any heat buildup.

[Verdadero Foe]

Some old games (made for DOS) had a functionality directly related to the CPU speed, they play super fast in more modern CPU. Classic old doom didn't had this problem.

In my case, the game Need for Speed 3 (IIRC) almosts melts my CPU, I never knew why.

[Dancso]

Most likely the lack of a frame rate limiter, where the engine just forcibly draws excess frames, not realising that the display device isn't even capable of handling them at such a pace.
The correct way to handle this is to ignore extra frames that go above refresh rate, probably even gametics (unless for example you're dealing with a multiplayer game where a constant gametic pace has to be kept). Some games might report that they run at hundreds of FPS but really it's just an approximation of how many frames it could thoretically process per second.

Usually this would involve taking a time stamp from the CPU before and after the frame (and/or gametic) is processed, gettng the difference and then seeing how many of that would fit into a second.