Jism It's proberly due to this bios on overclocking.guide/download/amd-radeon-rx-480-unlocked-air-bios/ which cranks voltage up to 1.4v & 225w tdp.

No not because of that ....Whilst a product (ie GPU) is considered "halo", driver will cross ref bios signature to see if ROM is unmodified.For example you'll see W1zzard asking the author of VBE7 in this post how he circumvented bios signature check.Then Hawaii had it for a period, then it was removed, see this thread from about post 32 the discussion occurs in a way. In that thread was where Hawaii bios mod occurred, prior to that you had only The Stilt's mining ROMs and Shammy's PT ROMs, both people that had access to getting ROMs signed.By the time Fiji bios mod was done bios signature enforcement was not there.Polaris did have it initially, then in driver Crimson v16.9.1 it was dropped, it has resurfaced now and will probably disappear again. Initially Lordkag of Fernado's WinRaid forum came up with a software patch for Polaris for drivers prior to v16.9.1 (I asked him and got some OCN members to test it), asder00 AFAIK knows how this mod was done, so he was able to sort it ASAP for Crimson ReLive :D (he has posted AMD drivers prior to release/modded ones on Guru3D ;) ).Lordkag has also created a UEFI/GOP module which works on modified AMD ROM when motherboard is in "pure UEFI mode" (ie CSM=Off). With some minor test results from me he created the custom UEFI/GOP. You just can't have Secure boot enabled as the UEFI/GOP signature has not been resigned to account for modification.