Stress testing CPU overclocks

ikt · February 12, 2015

Recently I made an i5-4690K build and I slapped on a Scythe Mugen 4. Finally got into overclocking again, where my last experience was with a Pentium 3 based Celeron. That aside, which programs and more importantly, which tests are suitable for stressing your overclock on a Haswell CPU?

You have Prime95. The new version uses AVX2 instructions which some people say puts an unreasonable amount of stress on the CPU for Haswell. It generates a huge amount of heat. The old Prime95 with version <= 26.6, don't use this instruction set and generally a stress test might register temperates of about 20c lower! This is a huge difference.

IntelBurnTest also seems to use this instruction set and generally also puts about the same amount of stress on the CPU like Prime95 does.

You also have AIDA64. With the stability test suite you can choose to stress specific components. From the post of an AIDA64 dev, the FPU stress test also uses AVX2 instructions. See the post here.

The results are as following, with the peak temperatures, on my Core i5-4690K @ 4.6GHz 1.285mV

CPU exclusive 65c. Seems to average out to 60c on the hottest core.

FPU exclusive 94c! Seems to average out to 91c on the hottest core.

CPU + FPU 83c. Seems to average out to 79c on the hottest core.

There's also Intel XTU which seems to be a somewhat lighter version of IBT, but with a much fancier interface. And OCCT, but I haven't used that.

As you can see, the temperature differences are absolutely ridiculous. 30c is a huge difference, from "Oh, another 50mV won't hurt to get that +100MHz stable" to "Shit, I might want to back down 100MHz or I'll fry it". Will regular non-production software ever use these instructions in the future? The heaviest things my computer ever runs are games, I'll probably never get into transcoding videos or use this build for anything 'professional', but it'd be nice to know how these affect you, if they do. How do you people test your overclocks and what's your testing methodology?

Please don't comment if all you have to say is something alike "Prime95 for 8 hours minimal" because you're not addressing the main issue here, of which part and how the CPU is stressed.

LogicalDrm · February 13, 2015

I can say I honestly didn't get half of what you were talking about. But then again, I'm happy with mild OC only. My current combo is IBT and OCCT. From these two OCCT stresses CPU much more because I got BSOD with clocks that IBT was showing stable. XTU is usually recommended to people new to OC as its rather easy and simple to use. I've done the benchmarking thing with it but not yet used it to OC validation at all.