How to use it?

[alsoijw]

There is some manual? I want reduce voltage on cpu. As I understand I have to do stress test. How can I check some pstate? When I run stress --cpu 8 I can see like that

Voltage ID encodings: SVI (serial)
Detected CPU model 65h, from family 15h with 4 CPU cores.

Core 0 | P-State Limits (non-turbo): Highest: 1 ; Lowest 5 | Current P-State: 1
 Pstate Status CpuFid CpuDid CpuVid CpuMult CpuFreq CpuVolt IddVal IddDiv CpuCurr CpuPower
      0      1     20      0     28  18.00x 3600MHz  1200mV    145     10  14.50A   17.40W
      1      1     16      0     54  16.00x 3200MHz   875mV    107     10  10.70A    9.36W
      2      1     13      0     70  14.50x 2900MHz   675mV     87     10   8.70A    5.87W
      3      1     11      0     78  13.50x 2700MHz   575mV     77     10   7.70A    4.43W
      4      1      7      0     96  11.50x 2300MHz   350mV     58     10   5.80A    2.03W
      5      1     20      1    110   9.00x 1800MHz   175mV     42     10   4.20A    0.73W
current      1     11      0     85  13.50x 2700MHz   488mV

What state I have to edit? How to switch to another state?

[echaskaris]

You modify the CpuVid field. Higher is lower voltage.

[wmarkow]

I have a few questions related to the output from @alsoijw:

• P-State Limits (non-turbo): Highest: 1 ; Lowest 5
  the non turbo P-states are from highest 1 to lowest 5. However below there are six states. The first one with 0 id - I assume that this is the turbo one, right?
• the first line Current P-State: 1 says that current P-State is with number 1 (or this 1 means something else?), however at the bottom it says
  current 1 11 0 85 13.50x 2700MHz 488mV
  which can give a clue - by looking at the 2700MHz frequency - that the current state is 3. In which P-State is current?

Edited: now I see that my question may be more related to #9.

[wmarkow]

I think I know what is going on, related to my question. It looks like amdctl doesn't correctly distinguish between turbo and non-turbo P-States. In the example from @alsoijw, his processor has probably three turbo states and four non-turbo and it should display like:

Core 0 | P-State Limits (non-turbo): Highest: 2 ; Lowest 6 | Current P-State: 1

More info in #9

[alsoijw]

I tried to reduce voltage, so I got some voltage value. I could open gedit and typed some text. But when I open video in firefox without hardware acceleration system crash, so I got black screen. As I remember stress utility continued work, non firefox.

Also I am interesting how can I test some turbo frequencies because they not always active. For example it can jump form 2700 MHz to 3200 MHz but I want test 2900 MHz.