Adaptive Vcore and AVX temperatures - A revelation!

So it's widely known that the Haswell VRM will automatically boost vcore when running AVX instructions. Usually, this is regarded as a Bad Thing (TM) but I did some testing tonight that doesn't quite fit with this thinking.

Until now, my preferred method of overclocking has been a fixed vcore and speedstep turned off. At 4.4 GHz, I've found that:
1.24 is required for AVX1, e.g. a 12-hour Prime95 run or Aida64 FPU test
1.28+V is required for Linpack 11 with AVX2 (it works at 1.24V, but BSODs every couple of runs).
With non-AVX loads, I could probably use a much lower voltage, but since the VCore is fixed, I have to set it for a "worst case" scenario.

1.28+V results in 90+C in Linpack 11 and I also have to make a choice – do I stick with 1.24V which works fine in everything else, or do I put in a needlessly high voltage just so I can run Linpack 11?

Today I tried adaptive vcore for the first time and dialed in +0.030V.

At 4.4 GHz, this results in
At full non-AVX load (e.g. Aida64 CPU test): 1.197V
In AVX/AVX2 tests: 1.273V

However, running Linpack 11, the voltage actually only hit 1.273V during very brief periods of time. Most of the time, it was actually at 1.197V. This resulted in a Linpack AVX2 peak temperature of 76C.

I think it's doing the same thing in Prime95. My Prime95 temps are now actually 75C with Small FFT's, vs 80C at 1.24V fixed before, even though Aida64 indicates a constant 1.269V.

Thanks to the very low non-AVX voltage, the Aida64 CPU-test temps are now ridiculously low and topped out at 52C now at 1.197V.

So far I've only done 10 minute runs of each stress test, so I can't confirm 24/7 stability. But so far, it looks *very* promising compared to the temps I was seeing with fixed Vcore. It almost looks like you can use the AVX voltage boost to your advantage by using a lower non-AVX voltage. It looks like Intel very obviously designed AVX2 with dynamic VCore in mind, only applying the +0.1V boost for a fraction of a second when it is required.

For 24/7, I run Adaptive Mode at 1.275v. My motherboard has two fields for adaptive mode: Offset, and "Additional Turbo Mode Voltage." I set Offset to 0 and this Additional Turbo Mode field to 1.275. As advertised, this means that for 3.9GHz and below, my voltage is stock. Whenever the CPU boosts to my 4.7GHz max turbo speed, or any speed between that and 3.9GHz, voltage jumps to 1.275v. My motherboard lacks a cache voltage probe, but I employ the exact same voltage setting for it as well, at a 4.5GHz overclock.

This 1.275v adaptive setting does increase to 1.391v as soon as I put an AVX load through it, so obviously I don't plan on encountering stress-test quantities of AVX instructions.

For me, there was a large difference between 1-3hrs of stability and 24/7. Adaptive 1.24v will run for hours, but eventually fail...I ended up working my way up to 1.275v in order to get rid of those BSOD. I'm curious if you find a similar behavior with your sample.

Going to try this out.

Did you compare Gflop performance between the voltage settings?

Very nice results with the temperature.

I obvserved the same behaviour with Prime/Aida and my daily work with FFmpeg which heavily utilizes AVX. During encoding sessions my vcore occasionally jumps from the base 1.205v im using to 1.232 and 1.248v but thats usually just for a split second, I call them AVX spikes.