One of the things I did to verify that my newly-built home PC was working well was to download and run a CPU temperature monitoring program, and leave that open in the secondary monitor while running programs in the primary monitor.
Unfortunately, this pretty quickly turned up problems. The CPU, an Intel Core i7-4790K, would get dangerously hot when running certain games. The game Cities: Skylines exhibited the worst symptoms: After running the game for just a minute or two, although the game itself would run great, the CPU temperature (as reported by the temperature monitor program) would shoot up to nearly 100 degrees C! That’s close to the point where the PC will shut itself off to avoid damage, and much hotter than I would expect.
I thought the problem might be due to my having done a poor job applying the thermal paste to my CPU and/or installing the stock heatsink incorrectly, so I removed the heatsink, carefully cleaned off the old thermal paste, applied new thermal paste, and reinstalled the heatsink. After doing that, though, the CPU temperatures while playing Cities were still extremely hot.
At this point, on the advice of some of the friendly folks at the Gamers With Jobs community, I decided to throw some hardware at the problem, in the form of a US $29 Cooler Master Hyper 212 EVO heatsink!
I’d previously never bothered with “premium” heatsinks, since I don’t overclock my systems (valuing rock-solid stability over an incremental speed boost). In this case, though, it seemed like the best option to protect the $340 investment I’d made in my nice CPU.
I’m very happy to report that it worked perfectly! With the 212 EVO installed (replacing the stock Intel heatsink, and with another fresh application of thermal paste), CPU temperatures while playing Cities: Skylines dropped from nearly 100 C down to the mid-40s C!
One caveat that I discovered with the 212 EVO though is that it fastens to the motherboard from both sides, effectively pressure-clamping itself down onto the CPU. Therefore, I needed to unscrew my motherboard from the case to install the new heatsink. If you’re doing a build that includes a premium heatsink, I suggest installing the heatsink and CPU onto the motherboard before screwing the motherboard into the case!
A final additional purchase I made was a cheap ($8) case exhaust fan, since the case I used didn’t come with one. I didn’t want the air inside my case warming up over periods of long computer use.
CPU cases evidently come with quite a few variants of screw mounting hole spacings. The distance between screw holes is not, as it turns out, the size of fan that you should order! I found the chart on this quietpc.com page very useful (and accurate!) in translating the space between mounting holes that I measured on the back of my case to the size of fan that I needed to order.