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xperia64/amd-gpu-windows-driver-errata.md

Created April 22, 2023 20:28
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AMD GPU Windows driver errata
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amd-gpu-windows-driver-errata.md

AMD's GPU drivers on Windows have some bad behavior when the card is not active or the primary display on boot. Specifically:

  1. Certain EXE names are hooked in the kernel driver, and they won't even begin running for 10-15+ seconds after you open them
  2. ULPS (Ultra Low Power State) is buggy when Windows is running with the driver loaded, but no displays are enabled on the GPU

Regarding 1:

  • Applications named Steam.exe, Origin.exe, or uPlay.exe among others get hooked by the kernel driver, presumably for some sort of game integration that I don't quite understand
  • I get the feeling this is potentially very outdated cruft, given that uPlay.exe is hooked (which no longer exists), while UbisoftConnect.exe is not
  • When your AMD card doesn't own the Windows primary display, this hooking delays launch of EXEs with these names for whatever reason
  • I have not found a complete list of these EXEs in the kernel driver binary; I'm thinking they may be hashed? There's another list in the binary in plaintext, but that doesn't correspond to this behavior
  • The name of the EXE is what matters here; I can copy notepad++.exe and name it Steam.exe, and its launch will be delayed too
  • The fix: locate your AMD driver's registry folder (the one with a bunch of KMD_ and PP_ keys among others, should be a folder named 0000 or similarly numbered); Add a DWORD named KMD_GameManagerSupport, and set it to 0; then reboot

Regarding 2:

  • On my Vega 56 at least, ULPS bugs out at least when Windows is running and the card has no active displays
  • It will remain on for ~20 seconds, then enter BACO for ~3 seconds, and return to and active state
  • While BACO technically pretty much turns off everything, this includes the fans; This causes the card to heat up hotter than if ULPS/BACO were disabled, as the fans don't have time to spin up and adequately cool the card
  • I've seen ~60-70C in this BACO-toggling state, compared to 42C normally
  • The fix: locate the EnableUlps DWORD your AMD driver's registry folder, and change it to 0; I don't know if it's necessary, but I also change the EnableUlps_NA string key to "0" as well; then reboot
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