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AVX Offset bug / 8700k / Z370 Extreme 4

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Spunky View Drop Down
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    Posted: 19 Mar 2018 at 12:13pm
Hey guys,

My spec is the following:

i7-8700k
Asrock Z370 Extreme 4
G skills 2x8GB 3200mhz CAS14
Cooler for the CPU is Noctua NH D15


I can run 5GHz AVX at 1,424V with temps reaching 90C and package power at nearly 330W(Prime 95 smallFTT).

However, I have found a sweet spot at 5Ghz with -2 Offset at 1.32V. Here is the bug I am experiencing. When I do a stress test, for instance, Prime95 29 small FTT. The CPU downclocks to 4.8 accordingly, however after I stop the test the CPU is stuck at 4.8Ghz even when there is no load at all and it never goes to 5Ghz again until next reboot. Even the restart is a bit suspicious. When I restart the computer, it shuts down(cuts power completely) for a moment and then starts again. Usually, when you restart, the computer does not cut the power for a moment(fans and lightning on the board are on). Also, I have observed that sometimes when executing AVX instructions in a stress test the CPU does not downclock. For instance, while running Intel Burn Test the frequency keeps at 5Ghz, however, the consumption is way lower (100-120W instead of the usual 200W+) and the Gflops are way lower than in a usual test(50gflops instead of 150). All that while the CPU is at 5Ghz and 100% utilization. It appears that those bugs happen only when utilizing AVX.

Have anyone observed such behavior?

Best Regards!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wardog Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2018 at 2:53pm
1.424v? Surely you jest!
Nothing here. Move on!

16,441 - https://www.3dmark.com/fs/13030306
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spunky Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2018 at 4:26pm

However, I am afraid of running this for more than 30 minutes as the temps get near the limit. The cooler is not capable of handling so much heat although I have put liquid metal between die and IHS and cooler as well. 

I want to get the same none AVX performance using the offset, however, it does not work for me. Multiplier just gets stucks sometimes until reboot.

I will try to work with the offset voltage but it also feels buggy.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wardog Quote  Post ReplyReply Direct Link To This Post Posted: 20 Mar 2018 at 12:06am
Personally, I think you need to dial back your OC some.

Until you get better cooling anyways.
Nothing here. Move on!

16,441 - https://www.3dmark.com/fs/13030306
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