I have 4 pcs of Vega 64 GPUs and I tried to use Oldcomer version of softpowerplaytable mod. Three of those Vegas worked well. I got about 1850 H/s per GPU, but one GPU has somekind of problem. If there is softpowerplay mod in windows register with that specific GPU, then I got blue screen with "THREAD STUCK IN DEVICE DRIVER" message at windows start up. On start up all other GPU initialized correct way with fast acceleration and decleration of blower. This problematic GPU blower accelerates and keep running on high speed till windows automatically restarts.
Everything worked well after I boot windows to safe mode and remove "PP_PhmSoftPowerPlayTable" instance from GPU 0004. I even try to change HBM clock rate from 1100 MHz to 1000 MHz and still get stuck with this one GPU.
I'm using integrated intel GPU for monitor. This is 0000 instance in [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\
0001 - 0004 are vega 64 GPUs.
I got about 7200 H/s with three vegas undervolted and this problematic one with stock voltage and clock settings.
I have a single Vega 64 that had the same issues. I ended up using the xslm spreadsheet that was posted a few pages back to create a series of custom .reg files and everything seems to be working well now - albeit at 925mV. Happy to share the settings I used if you pm me (saves cluttering the thread). Standard disclaimer of use at your own risk applies though - I take on no responsibility for failures.