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prime95 small FFT's passed but large and blend error.

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post #11 of 24 (permalink) Old 01-22-2019, 03:38 PM
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Try doing ram testing with 1 stick and see which one is causing problems.
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post #12 of 24 (permalink) Old 01-22-2019, 03:39 PM
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Quote: Originally Posted by Assirra View Post
Greetings

I got a i7 8700k overclock to 4.8Ghz with 1.260volt and it worked flawless for while now. Curious about stability i decided to run prime95 and see if it could handle it.
Now the results i got are making me question my memory might be bad.
Small FFT test went 24hours without any issue.
Large FFT test got rounding errors around the 17hour mark
blend test got rounding errors after about an hour.

Now considering the RAM usage in comparison when each test started to having errors i think my ram might be bad.
I also did a test with putting everything to stock without any OC or XMP and it still spewed out rounding errors.

Is my memory bad and do i just need new or is there something deeper going on?
EVERY time I've seen a rounding error in Prime95, it has been a memory issue, not a CPU stability issue. For me, it's always been an issue with memory speed/timings, not an IMC issue that might be helped with VCCIO voltage, but I don't know if that is true for everyone. In any case, I agree with the others that say this is a memory issue, not a CPU stability issue.

I'd suggest you immediately run some long durability memory tests with one or more of: RAMTest, PassMark's MemTest86, HCI MemTest or Google's stressapptest. You have to know you have stable memory before you can adequately test your CPU stability.

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post #13 of 24 (permalink) Old 01-24-2019, 12:15 AM - Thread Starter
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So overnight i let the passmark memtest run and when i came looking this morning i got greeted by this.
This is with XMP on.
Now for some reason i couldn't make it go further cause my KB didn't work anymore so can't see the actual summery but this is pretty bad right?

If i indeed need to buy new memory what are the recommendations for a asus z370-e mobo and 8700k?
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post #14 of 24 (permalink) Old 01-24-2019, 04:22 AM
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You could try the run with XMP disabled. Depending on whether or not XMP automatically sets voltages, you might get stability issues in some cases when IMC/IO voltages are at their very stock (even though not likely, because 3000er RAM isn't a deal for Coffee Lake-S - usually).

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post #15 of 24 (permalink) Old 01-24-2019, 04:43 AM - Thread Starter
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At work now but put everything on stock with optimized defaults in bios and started it once more. Will see the results in about 6 hours when i get home.
Edit: just got home and this greeted me.

Seems i indeed do need new memory.
Any suggestions for stable ram welcome. don't know enough about the subject just yet but for whatever it is worth it, this PC is almost exclusive used for gaming.
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post #16 of 24 (permalink) Old 01-24-2019, 03:10 PM
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Quote: Originally Posted by Assirra View Post
So overnight i let the passmark memtest run and when i came looking this morning i got greeted by this.
This is with XMP on.
Now for some reason i couldn't make it go further cause my KB didn't work anymore so can't see the actual summery but this is pretty bad right?

If i indeed need to buy new memory what are the recommendations for a asus z370-e mobo and 8700k?
Test #6 in MemTest86 is often the first one to fail. That means your memory is not stable. You can try increasing DRAM voltage (up to 1.45V) or increasing primary timings to see if that makes it stable. FYI, when running MemTest86, I often first run test #6 for 2-3 passes and if that fails, you get your answer quickly. If that passes, then I run 3 passes on all the tests as a more complete test.

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CPU offset voltage of -25mv, runs VRVout 1.240-1.313V on full AVX load, 1.225-1.275V on non-AVX load
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post #17 of 24 (permalink) Old 01-24-2019, 03:43 PM - Thread Starter
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Quote: Originally Posted by jfriend00 View Post
Test #6 in MemTest86 is often the first one to fail. That means your memory is not stable. You can try increasing DRAM voltage (up to 1.45V) or increasing primary timings to see if that makes it stable. FYI, when running MemTest86, I often first run test #6 for 2-3 passes and if that fails, you get your answer quickly. If that passes, then I run 3 passes on all the tests as a more complete test.
Even on complete stock? Surely it should be rock solid without any issues when you put it on default right?

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post #18 of 24 (permalink) Old 01-24-2019, 04:03 PM
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Quote: Originally Posted by Assirra View Post
Even on complete stock? Surely it should be rock solid without any issues when you put it on default right?
That depends upon what mode you're in. If you're not in a troubleshooting mode or what could I do to make this work, then you're perfectly fine to return the memory immediately if it won't pass MemTest86 on stock auto voltages with no XMP and you're perfectly fine to return the memory immediately if it won't pass MemTest86 with just plain XMP settings.

I was referring to what you would do if you were trying to troubleshoot and see what it could do and then decide if that was OK or not. If it has errors at 2133MHz or whatever the non-overclocked stock rate is, then it's either really bad memory or there's something else wrong in the configuration/hardware.

FYI, I've read that MemTest86 should not be run in "parallel" mode where it's using all cores at once because that relies on some threading libraries in the BIOS which have unknown stability issues themselves and aren't used once Windows loads (so aren't really relevant to Windows stability). I don't know you were using MemTest86 in parallel mode or not. I use a mode that cycles through each CPU, one at a time.

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CPU offset voltage of -25mv, runs VRVout 1.240-1.313V on full AVX load, 1.225-1.275V on non-AVX load
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post #19 of 24 (permalink) Old 01-24-2019, 04:03 PM
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I'm having the same issue with my 4790k. Small FFT will do 4.8 with 1.3v no issue. If I run Large FFT or Blend with any ram speed I'll get a watchdog BSOD until I up the vcore. No idea why yet.

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post #20 of 24 (permalink) Old 01-25-2019, 12:56 AM - Thread Starter
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Quote: Originally Posted by jfriend00 View Post
That depends upon what mode you're in. If you're not in a troubleshooting mode or what could I do to make this work, then you're perfectly fine to return the memory immediately if it won't pass MemTest86 on stock auto voltages with no XMP and you're perfectly fine to return the memory immediately if it won't pass MemTest86 with just plain XMP settings.

I was referring to what you would do if you were trying to troubleshoot and see what it could do and then decide if that was OK or not. If it has errors at 2133MHz or whatever the non-overclocked stock rate is, then it's either really bad memory or there's something else wrong in the configuration/hardware.

FYI, I've read that MemTest86 should not be run in "parallel" mode where it's using all cores at once because that relies on some threading libraries in the BIOS which have unknown stability issues themselves and aren't used once Windows loads (so aren't really relevant to Windows stability). I don't know you were using MemTest86 in parallel mode or not. I use a mode that cycles through each CPU, one at a time.

I just let it ran as it started from the USB, nothing selected since it autoruns once it boots from the USB so sadly i have no clue how it ran.
I might try to mess with the voltages but for safety get new memory just in case i mess something up.
So far whenever i overclocked my PC i never played with manual memory overclocking since from what i read it doesn't effect gaming performance.

Thanks for answering everyone btw. In the start i was scared that my fairly new CPU (8months old) might be dying but now i know better and i have learned some stuff as well.

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