Question Prime95 29.8 keeps failing Large FFT

Hi-Fi Man

Senior member
Oct 19, 2013
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Trying to test my RAM as I've been getting some BSODs lately and the farthest I can get is test 2 and then it fails with "rounding was x, expected less than 0.4". I rolled back the RAM (https://www.crucial.com/memory/ddr4/bls2k16g4d32aese) to 2400MT/s and all timings to auto and 2T but Prime95 is still failing around the same spot. CPU is stock ryzen 3700X with Noctua U12 and RAM has a small 40mm fan blowing over it; temps are all good. Is there an issue with Prime95 that I'm not aware of or is this RAM just bad?
 

aigomorla

CPU, Cases&Cooling Mod PC Gaming Mod Elite Member
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Download Memtest86 on a bootable usb.

Let it run overnight.
If it passes all 4 passes, you can rule out ram.
If it fails, it could mean a few things.. bad ram / bad compatibility with ryzen / bad board.
You would need an intel system to run memtest, or another system to rule out ram, if it fails memtest.
 

Hi-Fi Man

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Oct 19, 2013
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I've run memtest overnight and no issues.

Did some more fiddling and prime95 only fails (really quickly too, within minutes) when running with 3 threads or lower. I can run it just fine with 4 or more threads. I also tested with Intel burn test for a few hours on 2 threads set to 16GiB of RAM and no errors. When I first noticed the weird behavior with prime95 I thought it might be the whole idle bug with Ryzen that plagued my last motherboard. I've now disabled global C-state control in addition to the already set typical current power supply setting. I'm thinking about swapping the PSU if I get anymore issues but I don't know. This issue is driving me nuts.

I should also say that prime95 always fails on 1 thread within seconds of running it.
 

aigomorla

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Sounds like a board or CPU issue to me as well.

What PSU are you running?
 

Hi-Fi Man

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Oct 19, 2013
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Sounds like a board or CPU issue to me as well.

What PSU are you running?

I'm going to link to my follow up thread for some new findings.