I just build an old Gigabyte Vega 56 Gaming OC. Almost the time it works great. But sometime its fan runs at full speed, the monitor turns black but the music still plays! Look at GPU-Z's log file and I see its hotspot temp is 511*C !!! And the VDDC is < 0!!! Everything else works normal
My PC: I5 8600K, 16GB, Asrock z370m-pro4, Windows 10 pro 1903, Radeon driver v19.9.1. I use WC for this card and its temps are rarely go > 80*C
I had something similar with my vega card not same as yours.
Use DDU(google it) and then install the latest stable drivers and after that download the following tool, overdriventool.
Overdriventool is a handy tool that allows you to properly undervolt, set a fancurve, voltage, coreclock, memorycore and more.
Hope it works well!
I use the default Gigabyte's F5 BIOS, Wattman of some Radeon versions to undervolt, but it still crashes sometime, with hotspot temps always are 511 degree, not more not less. And sometime VRM temps is more than 2000 degrees but the card dont melt down or crash (only crash when hotspot temps is too high, with fan runs at full speed). Maybe it's driver's problem. This is from the latest driver 19.9.2
I would recommend you use overdriventool instead of wattman since I have only had trouble with wattman(seems like a vega problem overall with wattman don't know if it will ever be fixed). It sometimes reset overclock/undervolts and sometimes fans ramp up to max when the temps aren't even high.
I do not know what hinders you from downloading it and using it and running a few GPU stresstest to see if the stuff is working.
This is my settings I have undervolt and overclocked it.
You need to use the Reset button to return to your factory settings, because with these WattMan settings, the Vega GPU is difficult to operate stable. Using the overdriventool software, try to configure the WattMan settings so that the maximum GPU voltage is 1150 or 1100 or 1075...
It crash even when I dont use Wattman at all. And with 930mV I can run furmark and gamming for all day without crashing. But some times it crashes after 5 mins
I'm currently testing with your advice configs. Lets see if it crash again. Thanks