Real world benefit of FPU test?

[mikeyten4]

Hi everyone

 

I'm just wondring if someone can explain to me a little bit about the FPU test in AIDA64.  Until now I've been running stress tests with CPU, FPU, and cache being tortured.  As I understand it this is fine, but running an FPU only SST will applying the peak temperature to a CPU in order to show that it's capable of running under such circumstances without throttling back.

 

I've so far got a stable 4.2Ghz clock out of my 4770K and I'm going to move on (with a target of 4.4GhZ or 4.3Ghz).  At my 4.2Ghz clock the machine was stable for over 14 hours under AIDA64's CPU/FPU/Cache test and hit a peak temp of 75°c (on air).  It generally floated around 65°c-70° on all cores.

 

Following this I've just carried out an FPU only test under the same spec.  It peaked at 90°c on core 3, with the lowest peak on any other core being 81°c.  It didn't throttle (I believe the Haswell chips do this at about 95°c, TJMax is 100°c), but I stopped it after 15 minutes.

 

Now obviously the intention of a stress test is to put the machine under more or at least as much continuous pressure as real world use would.  Although my CPU didn't throttle, those FPU test temps are a bit higher than I'm really comfortable with.  I think I read somewhere that the FPU test uses AVX instructions, but I'm not sure if that's correct - truth is I don't know how it works to reach it's temperatures.  But what I really want to know is how representative of real-world use is it?  What sort of applications might push the CPU in the same way?  Many?  A certain set or applications in a particular professional field?  Are the results of this test alone something I should concern myself with if I've so far considered the same clock to be stable and safe under the full SST for over 14 hours?

 

If it helps, I'm running Windows 7 x64 and will be using the PC for music production, meaning it's heaviest load in real-world use will likely be Ableton Live plus a good handful of VST instruments and effects (creating and processing sound in real time).  Native Instruments VSTs will feature fairly heavily.

 

Cheers

Mike

[Fiery]

The FPU test puts a very heavy stress on the processor, both load-wise and thermal-wise.  It is a very unique test in a sense that not many other stress tests or applications are capable of pushing your processor that far -- using AVX, AVX2 and FMA instructions indeed helps AIDA64 to achieve that level of stressing.  Whether you deem it is useful for your particular usage scenario or not is completely up to you to decide   If you use AIDA64 to measure your temperatures while running applications or games, and you can see much lower temperatures than what you did while running the AIDA64 FPU stress test, then you may have some headroom in upping the CPU clock and/or voltage.

 

BTW, since only a handful of applications and benchmark software currently utilize AVX2 and FMA instructions, it is not easy to compare the amount of stress AIDA64 puts on your Haswell processor at this time.  But as soon as the new instruction sets become more popular, and software vendors keep pushing their optimization efforts even further, you will be able to see very heavy load being put on your processor while e.g. encoding a video stream.  So in our opinion AIDA64 FPU stress test is very much relevant, since it faces your CPU with the worst case scenario imaginable.  If it can stand that, then it's a good configuration (ie. both hardware and software settings are proper).

 

Regards,

Fiery

[mikeyten4]

Ok, thanks Fiery

 

So, what I've really taken from that is that I can monitor my real-world usage via AIDA64 to see how it compares... but even if everything is fine right now, more applications may start to use things like AVX instructions in the future, so my FPU result might be a sign foretelling what I could see in the future via real-world use.  The CPU copes with it at my current clock, but in honesty I can't see it being very healthy.  I guess I'll just have to keep an eye on things over time and see what the future holds

 

Thanks again!