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Prime95 blend and large fft fails but small fft doesn't

Shakecip
Level 10
I facing this problem in prime95 in small fft test passed and in large fft and blend worker 4 fails. My cpu is 6700k, asus maximus viii hero and 16 gb corsair 3000 mhz and I have the latest bios 2001.

In blend test worker 4 fails about 30-45 minutes and in large fft in 13 minutes. I have no overclock just the xmp profile settings.

I tried memtest86 for 15 hours and no errors. My maximum cpu temperature is 63 degrees and voltage reaches maximum at 1.186v.
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Nate152
Moderator
Hi Shakecip

With your cpu at default settings I suspect your ram is failing the test. Memtest86 is probably not the best tool for testing your ram, try HCI memtest or google stress app.

Try these settings on the Extreme Tweaker tab:

cpu vccio voltage 1.15v - 1.25v
cpu system agent voltage 1.15v - 1.25v

Does it pass the test by raising these voltages?

Shakecip
Level 10
i will try that and see how it goes and i will get back to you and in the meantime i have a question why if i set to adaptive mode and aditional turbo core at 1.220v in stress test doesn't go higher than 1.186V and if i install asus ai suite 3 and there i am not changing anything then the voltage rises up to 1.214V in stres test, so the voltage rises just for that that i installed asus ai suite, it is crazy.

I am comming with an update it seems that i raised cpu vccio voltage and cpu system agent to 1.25v and i have been running for an hour Large fft test and for now it didn't failed. What does this mean? That i have a bad memory controller or cpu is bad? Can you explain to me please? Should i leave it with this settings?

Nate152
Moderator
It means it's looking like your pc is stable. 🙂 You're hardware is fine, default ram speed is 2133MHz and anything over that is overclocked, the voltages you raised gives more voltage to the cpu's Integrated Memory Controller to help stabilize high speed ram. 1.25v is fine but you may not need that much, you can fine tune them by lowering the two voltages .01v one at a time until it fails the test then bring the voltage back up .01v - .02v then fine tune the other by doing the same. If it's working with both voltages at 1.25v you can leave them there but fine tuning it with lower voltages may lower cpu temps a little.

I don't use AI Suie, I use ROG CPU-Z or HWinfo to monitor voltages, CPU-Z is probably the most reliable for monitoring cpu voltage.

Install ROG CPU-Z and see what it's reading, don't run AI Suite make sure it's closed.

Near the top of this page in black click "setup" in the ROG version then click download now then click run.

http://www.cpuid.com/softwares/cpu-z.html#version-history

What voltage is CPU-Z showing?

Shakecip
Level 10
For monitoring i use cpu-z and in prime it shows voltage 1.136v. I tried something else to see if its stable i reset the bios again and i put in xmp and the memory at 2800 Mhz and it still fails without modifig cpu vccio voltage and cpu system agent voltage. It can't be stable even at 2800 mhz? Is strange, no?

Nate152
Moderator
Sometimes you'll get better results setting your ram manually rather than using XMP. It's not strange to have to tweak ram above 2133MHz, you just have to give it what it needs.

Shakecip
Level 10
So is not a weak memory controller or bad ram?

Nate152
Moderator
Nope your ram and cpu are fine, have you tried fine tuning the voltages to see if you can get them any lower?

Shakecip
Level 10
Look here i have a print screen how my cpu works in XMP mode in idle my voltage is static 1.248v and in load the voltage it decreases to 1.184 - 1.161v and to get in idle at 0.730v how is normal i need to set it from auto to adaptive in order to decrease the voltage in idle at 0.730v. Do you understand now what i mean? How normal is this under load the cpu to undervolt?

Well it's not normal for it to undervolt that much, normally it will overvolt some but it's not a bad thing if you're stable with 1.184v.

To get the voltage to drop at idle use adaptive mode as you did and let the windows power plan set to balanced.. I would discard the static 1.24v reading after switching to adaptive mode, if it's still only drawing 1.184v in adaptive mode and you're stable that's very good, this shows you likely have a good overclocking 6700k. 🙂