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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

Cases and Cooling Mod PC Gaming Mod Elite Member
Super Moderator
Sep 28, 2005
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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

Senior member
Oct 19, 2013
590
112
106
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

Cases and Cooling Mod PC Gaming Mod Elite Member
Super Moderator
Sep 28, 2005
18,199
931
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Sounds like a board or CPU issue to me as well.

What PSU are you running?
 

Hi-Fi Man

Senior member
Oct 19, 2013
590
112
106
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.

 

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