Thank you rednoW for sharing your reg file. Its the first where iam able to boot into Windows. Both Vega56 with 64 Bios runs at 2kh/s with ~140W for a minute or two and then the AMD Tool crashes or one GPU crashes and resets to default settings. Also if i reduce mem to 950mhz and rise voltages to 1100mV its unstable. Bad luck in silicon lottery?
Did you set target temp to 50-55 degrees?
Also you may need to fine tune fan speed. HBM @ 1150mhz will work only if its tempis below 65 degrees.