Originally Posted by matthew87
Anyone able to clarify the difference between VID and VDDC for Polaris?
Grabbed myself a RX 580 and confused as to how to measure vcore.
XFX 580 GTS Black Edition
NCP81022 GPU Voltage = 1.294v
VDDC GPU Voltage = 1.288v
I assume it's best to take the reading from the NCP81022 as that's the VRM controller?
I thought AMD 580s were hard locked around 1.20-1.25v, yet my card is pulling almost 1.3v with 50% power limit and a slight bump to GPU clock speed. This normal? Half the info i read on the net suggests a GPU core voltage of 1.25v to be around maximum recommended on air, yet my card is exceeding that without me even touching voltages.
I take it VID 1.2, the NCP is then set with some form of offset that determines actual voltage?
My card had some intermittent occurances of the display going blank.
Try a different display port cable or port on the GPU. That was the cause of my issue.
I had the XFX 580 GTS, I don't know if the black edition one. And it had a voltage offset of +100mv. The actual voltage is NCP81022 GPU Voltage and VDDC GPU Voltage, I suppose both are the same voltage, but measured in a diferent way.
You can see in the attached images, the voltages it had, the firestrike score and with hwinfo the actual voltages it was using. You can see that the vddc voltage is higher than the VID, so it was using a voltage offset. And like you can see in the last image, I could pass firestrike with a -150mv offset, but for games was only stable with -120mv.
Originally Posted by Ansau
And yes, Polaris tends to come with some offset for voltages, usually +50mV, which makes sense for you: 1.25V VID + 50mV - small Vdroop = 1.288V
The problem in this XFX 580 about the voltage offset is that it is not present in the VOI, maybe is present in xfx gpus controlled by the IR3565, but in NCP81022 ones is not, like you can see in the VOI:
1C 00 03 01 01 07 0C 00 0E 00 00 00 00 00 00 00 04 07 0C 00 0E 00 00 00 00 00 00 00
So I don't know how is this voltege offset added. And the usual bios VOI voltage offset mod, is blocked by default, can't be done without changing other bios tables and increasing the bios length. Also it have some missing values in some tables that I have no idea of for what are used for, so I din't had tried to do the mod to see if it was working.