I finally found a copy of amdvbflash.exe and installed it. I copied the modified rom into the same folder as amdvbflash.exe. I succeeded in unlocking the GPU. However, when I try to flash the modified rom, even though I have carefully created the modified file following your instructions, I get this error:

-f option not supported in external version of the tool. Please refer to tool help for list of option supported
Old SSID: 5701
New SSID: 5701
BIOS authentication signature mismatched.

   ERROR: 0FL01


Any suggestions on how I can flash the modified BIOS?