I have reluctantly started to use KDE4 on my main machine, and it's doing something that makes me crazy:

It runs hot. It runs ridiculously hot.

When I was running KDE 3.x I would use ktemperature to monitor my laptop internal temperature while I running applications vs. while I was playing games. kTemperature is nice little app because it doesn't take up much room (it docks on the system tray) and it's pretty easy to use. When I started using KDE4, I learned that kTemperature still worked -- so I've had the opportunity to compare the internal temperature of my laptop while I was running KDE3 vs. the internal temperature of my laptop while I'm running KDE4.

When running KDE3, the idle temperature of my laptop (that is, the reported temperature when I wasn't doing much of anything at all) was about 38 degrees Celsius.

When running KDE4, the idle temperature of my laptop is anywhere from 45-48 degrees Celsius.

But that's not all -- when actually doing things with KDE4 my temperature frequently spikes up to 78-90 degrees Celsius -- it used to be that only happened when I was playing games that required 3d rendering or a lot of CPU activity, but now it happens A LOT.

I initially suspected that it had something to do with the desktop effects, but I've since deactivated all of KDE4's desktop effects (arguably the most fun part of KDE4) and it still happens. Why does this happen? Why is KDE4 so much more heat intensive than KDE3? Is it really a good idea to create software that will contribute to the heat death of a rather expensive piece of machinery faster than previous versions of that software? Is there any way to fix this on my end?

These are all good questions. I have no good answers. But I do have this warning: KDE4 makes your machines run hotter by at least 7-10 degrees Celsius, and frequently 30-40 degrees hotter than that.