Disabling CSM in bios causes black screen on login

[archvile]

I have 3 displays connected to my GPU, all with DisplayPort. Just as macOS boots up, my screens go to black and I have to reset. It works fine with 2 displays connected.

I found out that enabling CSM in bios fixes the issue for me. Maybe it helps some other people as well.

Although it sucks that when CSM is enabled, post screen and clover is really ugly because of the low resolution.

 

[Mork_vom_Ork]

I could confirm this, too.
Have made the same expiriences with just two installed AMD GFX cards. If i enable CSM, i got high resolution (1920x1080) CLOVER but black screen after verbose boot - no login possible, no ARD connection possible via MacBook.

If i disable CSM, resolution was downscaled to 1280x800 on a 1920x1080 monitor, but screen does not fall into sleep after verbose boot - it boots right into the desktop.

Never had this effect with an AMD R9 280X when using this card as single GFX solution.
Right now i use AMD HD6570 in slot#0 and RX460 in slot#4 (to have both cards detected as PCIe16x)

 

[tikiss]

I have 3 displays connected to my GPU, all with DisplayPort. Just as macOS boots up, my screens go to black and I have to reset. It works fine with 2 displays connected.

I found out that enabling CSM in bios fixes the issue for me. Maybe it helps some other people as well.

Although it sucks that when CSM is enabled, post screen and clover is really ugly because of the low resolution.

Hi,
did you solved this problem?
I have quite the similar problem, main monitor (4k) connected over DP and the secondary monitor (Full HD) also over DP connected, the third device (TV) connected over HDMI.
If I enabling the CSM in BIOS my build is able to boot, but the Clover shows on the secondary monitor with (I guess) 1920x1080 resolution if the CSM is disabled the 4k monitor shows the clover with 4k resolution but I got black screen every time before the login screen gets visible.
I have tried if I disconnect the TV and secondary monitor my hackintosh is able to boot correctly.

Do you have any idea how can solve to solve the 4k monitor as primary for Clover and use native resolution?