i5 4670k Temperature fluctation during Prime 95 Blend stress test

My Build:
CPU - I5 4670K (stock settings w/ turbo enabled I think)
Heatsink - CM Hyper 212 EVO (w/ stock thermal paste). 1 fan attached
Motherboard - Asrock z87 Pro4
GPU - none
Case - Corsair 200r
case fans - two. Exhaust to back

Hello everyone,

I was getting high temps a few days ago and decided to update my bios/UEFI with the built in update manager. Afterwards, I ran Prime 95 again with the Blend Test. Things started out pretty well and the temperatures of all my cores sat between 48*C and 54*C (maximum at 56*C for first core) for about 15-20 minutes. That's how long it took for the first test to run.

Then test 2 started and, after 30 seconds, my temps shot up to the low 60s, going as far as 66 *C. before dropping down to 58*C-64*C. I stopped the second test after it ran for about 5 minutes.

Now I know the blend test is supposed to test other components like ram, but my CPU ran at ~100% load during both tests so why would my temps be higher in the second test. If anyone can provide me with some insight, I'd really appreciate it.

Thank you for reading and have a great day.
5 answers Last reply Best Answer
More about 4670k temperature fluctation prime blend stress test
  1. What are your voltage values during these tests? Prime95 tend to increase the core voltage (if it's set to adaptive) in some tests due to AVX load. So check if the values are increasing.
  2. I used CPUID and the voltage mostly hovered around at 1.14 V, sometimes dropping to 1.05. My clock is 3.6 ghz during the stress test I believe.
  3. Best answer
    That slight temperature fluctuation is kind of normal if the voltage is changing between 1.05v and 1.14v since Prime95 is using AVX and it is increasing the voltage if you are using adaptive voltage (which is the default setting for most z87 mobos). Adaptive voltage is a good thing though. It drops the voltage to low levels when there's no load. Great for energy saving and cpu stability.

    Try Intel Extreme Tuning's stress test (and also another monitoring software like HWInfo or HWMonitor to double check voltages and temperatures). It's not using the AVX in its stress test so most probably your voltage will be around 1.05v and the temperatures will be lower. Also monitor your voltage while playing games etc.. Basically Prime95 is the most unrealistic torture test. You shouldnt bee seeing this kind of voltage and temperature fluctuation in real life at all.

    And yes, looks like Turbo Boost is on but enhanced Turbo isn't. If you want a little bit more cpu performance you can activate it from BIOS. It basically enables the maximum Turbo Boost for all cores. So you'll end up at 3.8 GHz but also slightly more voltage and temperature. Actually Turbo Boost isn't really efficient. Since it's using more voltage than it actually needs. You can easily reach to 4.2 GHz with these voltage values if you have a decent cpu chip.
  4. Thanks for your response. That was very helpful. I will try all these suggestions and post back what I find. Thanks again.
  5. Thanks for your response. That was very helpful. I will try all these suggestions and post back what I find. Thanks again.
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