Cannot disable CSM on B450M PRO4

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   Hi, 

I want to disable CSM on an ASRock B450M PRO4 with BIOS version 3.90 and Sapphire Radeon RX 570 8 GB PULSE. When I disable CSM in the boot menu, save changes and restart it will be enabled again after restarting. The restart after disabling takes longer than usual and the fans spin up several times. The screen stays off for a short while. The AS Rock image at boot is displayed at high resolution when having the display attached to a display port, but not when attached to a HDMI port. When entering the BIOS however it is displayed in 1024x768px even though FULL HD is enabled in the setup. That's why I'm suspecting not being able to disable CSM has something to do with the VBIOS and GOP support, but a Radeon RX 570 should support UEFI boot just fine. 

Thanks!

Complete build
[URL=https://pcpartpicker.com/list/xcYd7T]https://pcpartpicker.com/list/xcYd7T[/URL]

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CTB Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 11 Jun 2020 Status: Offline Points: 4	Post Options Post Reply Quote CTB Report Post Thanks(0) Quote Reply Topic: Cannot disable CSM on B450M PRO4 Posted: 11 Jun 2020 at 2:00am
	Hi, I want to disable CSM on an ASRock B450M PRO4 with BIOS version 3.90 and Sapphire Radeon RX 570 8 GB PULSE. When I disable CSM in the boot menu, save changes and restart it will be enabled again after restarting. The restart after disabling takes longer than usual and the fans spin up several times. The screen stays off for a short while. The AS Rock image at boot is displayed at high resolution when having the display attached to a display port, but not when attached to a HDMI port. When entering the BIOS however it is displayed in 1024x768px even though FULL HD is enabled in the setup. That's why I'm suspecting not being able to disable CSM has something to do with the VBIOS and GOP support, but a Radeon RX 570 should support UEFI boot just fine. Thanks! Complete build [URL=https://pcpartpicker.com/list/xcYd7T]https://pcpartpicker.com/list/xcYd7T[/URL]

CTB Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 11 Jun 2020 Status: Offline Points: 4	Post Options Post Reply Quote CTB Report Post Thanks(0) Quote Reply Posted: 11 Jun 2020 at 5:22am
	I changed the DUAL BIOS switch on the Sapphire Radeon RX 570 from Compute Mode to Gaming Mode. Now it works. It does not seem to be documented anywhere that Compute Mode equals Legacy Mode instead of UEFI.