Setting CPU and GPU not working

[hubyhuby]

I have a Thinkad E590 running Ubuntu 18.04 LTS + Intel i3 8145
The setting does seem to work, but the values are not taken into account by my system:

For exemple this Dumb value may be set :
undervolt 0 'CPU' -800.84
undervolt 1 'GPU' -800.84
undervolt 2 'CPU Cache' -100.84
undervolt 3 'System Agent' -120.84
undervolt 4 'Analog I/O' -120.84

Obviousely -800mv seems impossible, but all seem to go find and the read command "reads" the bios values as setted correctly...

Only the 'CPU Cache' value seems to do something, since when I play below - 100 mW it crashes my system.
I am running a 3D game to do the tests

[hubyhuby]

This parameter seems to work, as it crashes after -140mv like this one :
undervolt 3 'System Agent' -160.84

[velovix]

I'm seeing similar behavior on my XPS 15 9570 running an i7-9750H. The CPU undervolting setting doesn't appear to have any effect. Even if I set it to unrealistically low values, the system behaves normally.

[smopucilowski]

I'm seeing similar behavior on my XPS 15 9570 running an i7-9750H. The CPU undervolting setting doesn't appear to have any effect. Even if I set it to unrealistically low values, the system behaves normally.

Could you elaborate please @velovix? I'm also using an XPS 15 9570.

[velovix]

@smopucilowski I edited the CPU line in /etc/intel-undervolt.conf, decreasing the voltage in 50 mV increments, running sudo intel-undervolt apply each time. I didn't see any changes in stability even when running the stress stress test even when going down to -600 mV. This is when I suspected the voltage of the CPU was not being changed. If there is any more information I can provide, I would be happy to!

[velovix]

I'm now unable to reproduce this issue. Undervolting seems to work as expected. I don't know what's changed.

[spfanning]

On my i7-6650U only the higher voltage of undervolt 1 and undervolt 3 has an effect on the GPU. I have read that on some processors only the higher voltage of CPU Cache and CPU is applied but I haven't tested this on my CPU.

[benklop]

I can confirm this issue. when watching the output from i7z while tweaking values, I do not see a corresponding decrease when tweaking things.

[bradsoto]

It seems Intel microcode updates disable undervolting, but show changes to the msrs. The changes will have no effect for CPU or GPU, but work on cache. On my hardware there is no easy way to revert to older microcode.

[hibby50]

On my 10310u I am seeing the same. I did 0 CPU -1000 just to confirm and the system stayed up

[S-trace]

On the i7-8750H (DMI: ASUSTeK COMPUTER INC. TUF Gaming FX705GE_FX705GE/FX705GE, BIOS FX705GE.307 02/08/2021) if I set impossible CPU Cache undervolting to -1000 mV my system instantly hangs up (as expected), but if I set the CPU or GPU undervolting to impossible -500 mV - the system does not hang and GPU power consumption (both in intel_gpu_top and (as the uncore) in the intel-undervolt measure) remains same.
I have the following CPU:

model name      : Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz
stepping        : 10
microcode       : 0xea

I have removed the microcode upgrade from my system (sudo mv /usr/lib/firmware/intel-ucode /usr/lib/firmware/intel-ucode.bak; sudo update-initramfs -c -k all), this reverted my system to microcode version 0xca but GPU undervolting still does not work (I set impossible -1000 mV GPU undervolting, but the system works fine after intel-undervolt apply, and intel-undervolt read shows GPU (1): -1000.00 mV.

I have downgraded the BIOS to FX705GE-AS.305 which downgraded the CPU microcode to version 0xb4 - and still have the stable system with an impossible configuration like this:

undervolt 0 'CPU' -500
undervolt 1 'GPU' -500

I have no easy way to continue downgrading my microcode (but I have a FX705GE-AS.301 BIOS dump for programmer).

[bhupinderdeol]

my DELL E64XX reading are below:

sudo intel-undervolt apply
CPU (0): Input/output error
GPU (1): Input/output error
CPU Cache (2): Input/output error
System Agent (3): Input/output error
Analog I/O (4): Input/output error

laptop became very fast though