Encountered weird behaviour while undervolting my i7-8665U

[unclewebb]

same value

I would start testing with the Intel GPU and iGPU Unslice set to the same value. If you get better results setting these two offset voltages to different values then set them to different values.

On many CPUs, if you set the Intel GPU offset to -50 mV and you leave the iGPU Unslice offset at 0 mV, this undervolt will not do anything. Even if you set the Intel GPU to -500 mV, it still will not do anything until you start adjusting the iGPU Unslice.

I have not done a lot of experimenting undervolting the Intel GPU or iGPU Unslice. If your computer has a Nvidia GPU, undervolting the Intel GPU and iGPU Unslice will not reduce power consumption any meaningful amount. Same goes for adjusting the System Agent. If lowering the voltage of anything does not change power consumption or temperatures then I would not bother. You can end up creating instability without accomplishing anything.

The core and the cache are always going to be the two most important offset voltages to adjust. They give the biggest improvements; either better temperatures or better performance or a little of both.

 

[WhenMusicAttacks]

I do mostly hackintosh laptops and they only have the igpu activated so i feel like undervolting everything The results are always great. Of course same applies to windows. Sadly one of my go-to tools for windows testing, Sisoftware sandra, is recently crashing on me even at stock settings in the GPU testing section on every machine. Dunno if it's a new windows bug

 

[hkgute99]

Hi, do you mean same value? As i undervolt maybe 10 machines every week - even though most using voltageshift on macos, but the same applied in windows with throttlestop - the usual pattern for intel skylake based machines (so up to 10th nn G) seem to be CPU and iGPU highest value around 150, cache and igpu unslice about 90 and then system agent around 70.. so igpu unslice is much lower than actual igpu itself. In voltageshift i have it named as "Analogy I/O" though

@WhenMusicAttacks, I am interested in undervolting my iGPU. Since you undervolt "maybe 10 machines every week", any idea how much an Intel UHD 620 (Whiskey Lake) can go down to, both GPU core and unslice?
And also is there meaningful gain in gpu performance by undervolting? Also is there any way to increase even a bit of performance from iGPU by adjusting any power limits?

@WhenMusicAttacks also can you tell software that could be used for testing GPU stability during undervolting.

 

[WhenMusicAttacks]

@WhenMusicAttacks, I am interested in undervolting my iGPU. Since you undervolt "maybe 10 machines every week", any idea how much an Intel UHD 620 (Whiskey Lake) can go down to, both GPU core and unslice?
And also is there meaningful gain in gpu performance by undervolting? Also is there any way to increase even a bit of performance from iGPU by adjusting any power limits?

@WhenMusicAttacks also can you tell software that could be used for testing GPU stability during undervolting.

Usual for 8250 8265 i get 180 core, 180 igpu, 90 cache, 90 igpu unslice, 70 system agent. range i would say is 220 - 150 for the first two values. I would say the pattern is very consistent with igpu and cpu being very similar, igpu being maybe sometimes a bit lower voltage - higher value for the negative offset - maybe 180 core will do 190 igpu, and igpu and cachebeing very similar and around half the core

there are no huge gains in benchmarks as they only stress gpu alone, keep in mind the best thing for igpu is dual channel memory at the highest possible frequency

i found that Unigine Superposition crashes easier than 3dmark

 

[WhenMusicAttacks]

this is what else i do when i refurbish these before turning them into hackintosh!