CPU and iGPU undervolting not working on i7-7500U

[HorstBaerbel]

I turned off secure boot now, but only the third parameter is doing something for me. I tried:

sudo ./iuvolt -800 -800 -90
wrote 0x8000001199A00000 successful to plane index 0
wrote 0x8000011199A00000 successful to plane index 1
wrote 0x80000211F4800000 successful to plane index 2

but the system does not crash as expected (-800 should be chosen) ;) So the first two parameters do nothing on my system. The cache parameter does work though and crashes my system at -110. Another issue is that:

sudo ./iuvolt 0 0 0
wrote failed, got: 99a00000
wrote failed, got: 99a00000
wrote failed, got: f4800000

seems not to be working.

EDIT: And I've found a strange effect: sudo ./iuvolt -1 -1 -90 or sudo ./iuvolt -90 -1 -1 Have no effect on temperature and performance, but sudo ./iuvolt -90 -1 -90 does. Making the CPU undervolt smaller than the cache undervolt, again, does not change anything though... :/

[koriwi]

same for me. on my 8550 i cant set it to 0 0 0. when i want to do that, i disable iuvolt and reboot

[tiziw]

The CPU core and cache share the same voltage plane. If different values are chosen for both, the highest out of the two will be chosen. Meaning if you undervolt with values -1 -1 -90, the actual undervolt will be -1 since it is the highest value. Same counts for the other example where you did an undervolt with values -800 -800 -90.

I'm not sure why the iGPU undervolt didn't work are you using external graphics?

[HorstBaerbel]

The CPU core and cache share the same voltage plane. If different values are chosen for both, the highest out of the two will be chosen. Meaning if you undervolt with values -1 -1 -90, the actual undervolt will be -1 since it is the highest value. Same counts for the other example where you did an undervolt with values -800 -800 -90.

Ok, if "highest" means positive infinity it makes sense (I though it would mean "highest undervolt"). Would be good to fix the zero bug though. I'm not using any external graphics.