i9-13900HX support

[adamdicarlo0]

cpu family  : 6
model       : 183
model name  : 13th Gen Intel(R) Core(TM) i9-13900HX
stepping    : 1

[evertvorster]

Yes, please add support for this CPU, it's getting heavily throttled.

[adamdicarlo0]

From what I'm seeing online, it sure sounds like most PC firmware locks newer CPUs (including this one) from being undervolted. I've tried intel-undervolt and it's unable to undervolt this CPU. I'm on a System76 addw3 (Adder WS) running coreboot, though, so it seems surprising that System76 would disable it. Haven't looked more into it yet.

[alexis-belmonte]

Can confirm that my CPU won't go past the ~50W TDP barrier, as shown in turbostat:

# turbostat --quiet --interval 1 --cpu 0-31 --show "PkgWatt","Busy%","Core","CoreTmp"
Core    Busy%   CoreTmp PkgWatt
-   97.03   64  47.62
0   75.23   63  47.55
0   97.37
4   85.45   61
4   97.66
8   89.96   63
8   95.96
12  94.64   63
12  96.92
16  95.98   64
16  97.12
20  97.21   61
20  96.93
24  97.93   62
24  97.64
28  96.38   61
28  98.34
32  99.70   64
33  99.74   64
34  99.73   64
35  99.67   64
36  99.73   64
37  99.70   64
38  99.66   63
39  99.70   63
40  99.71   64
41  99.49   64
42  99.72   63
43  99.71   63
44  99.06   63
45  99.55   63
46  99.54   63
47  99.62   63

I also personally tried to pass ACPI OSI strings, but to no avail -- FYI I've tried Windows 2022 and Linux, both did not do a difference.

A bug report has been opened on the kernel.org mailing list regarding this issue.

[evertvorster]

The "HX" variant of the i9-13900 CPU is actually physically unlocked, but it is also used in laptops, so there is reason to believe that it should be able to be undervolted.

As for power consumption, my Sager NP8875 E on powersave mode draws a constant 104W in turbostat when running s-tui in stress testing mode, and I have seen a 215W total system draw in s-tui in performance mode yesterday... So 50W is woefully too little power to draw for a system with this CPU.

As monitored by turbostat, I can get an instantaneous power draw of 142W, and a constant power draw of 120W under load.

This CPU is also able to keep at least one core at 5.4GHz (Full turbo mode) and draw about 40W.

[evertvorster]

On aside note, how does one find out what the various powercaps should be for a system and CPU?