I'm having some interesting temperatures on a Core i7 4790k I'm working with. I noticed that idle temps were ~80-90c and found that the CPU fan seized due to a tightly wrapped cable around the fan.

The fan ran pretty rough and uneven after I fixed the tight cable, so I replaced the heatsink and fan with a Coolermaster Hyper 212 EVO (which I've had great success with in the past) and applied Arctic Silver 5.

The idle temps are down to ~30C now, but under a Prime95 stress test (max heat) they instantly go to ~100C. Is it possible that something is damaged in the CPU? The stock fan was probably seized for many months.

1 Answer 1


Current versions of Prime95 are known to create extreme temps in Haswell/DC processors. It's recommended to avoid that test... I know I would!

Apparently it uses the FPU with extreme intensity and this leads to the high temps.

So to that extent don't worry it's "normal" :)

  • Any idea on how much the year and a half with no fan will decrease the CPU life?
    – jonesy827
    May 3, 2017 at 18:32
  • Impossible to tell I think. I might guess that if it's not fried then likely it's not damaged at all, but who could know for sure. May 3, 2017 at 18:46

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