Gpu voltage lower than set

[andrewtjb]

Checklist

• The problem is not listed in the hardware support matrix as a known limitation. Examples of known driver-side issues are fans not turning on with a custom curve or inaccurate power limits on RDNA3.
• I've included a debug snapshot if the issue is related to hardware configuration

Bug description

LACT-v0.7.0-snapshot-20250210-174101.tar.gz

Hi

I've noticed an issue with the voltage you actually end up with being lower than what was set.

I noticed that I was getting crashes when using the same undervolt settings I was using under windows and after some testing I figured out the problem was due to the voltage being lower than set.

For example, under windows I always use 2000mhz and 1060mv but using this setting with LACT actually gives me around 1030mv so it crashes but if I set it to 1090mv then I get closer to 1060mv.

System info

- LACT version: 0.7.0
- GPU model: AMD Radeon 5700XT
- Kernel version:CachyOS x86_64
- Distribution: CachyOS x86_64

[ilya-zlobintsev]

Does this happen when the GPU is running at max clocks or below? If it's running below 2 GHz, this sounds normal as it's using a value lower than the highest curve point for both voltage and frequency:

OD_VDDC_CURVE:
0: 800MHz 750mV
1: 1437MHz 819mV
2: 2000MHz 1090mV

[andrewtjb]

This is happening at max while stress testing and I've maxed the power limit to avoid it throttling.

The frequency while testing is around 1950mhz which is normal for this GPU as it's always about 50mhz less than what you set it to.

Under windows with the same settings during stress testing I get 1950mhz but with the actual voltage I set.