GTX 980 ti, DP + DVI = black screen. (Sierra 10.12.1)

[cnrd]

Hi

 

I have a fully working Sierra system, except for a single annoying problem:

 

Whenever I connect a DP and a Dual Link DVI monitor, both screens go black at second stage of boot. (Like they would without AGDPFix).

 

If I connect a DP or a Dual Link DVI monitor, everything is working just fine.

 

If I use a DP + DP -> Dual Link DVI adapter, everything is working just fine (Except the adapter being unstable, but same thing happens on MacBook).

 

I have not tested a normal DVI monitor + DP monitor.

 

If I connect either DP or DVI monitor after getting to desktop, both work fine until reboot.

 

Both monitors are 27" 2560x1440.

 

I'm injecting my 980 ti as GFX1 using an SSDT with a MacPro6,1 sysdef and I have already tried changing the sysdef to iMac17,1; iMac15,1; and iMac14,1.

 

Both monitors were working fine with El Cap 10.11.6.

 

Anyone have any ideas on what to try to fix this?

[voin]

Same issue. I have GTX960. Digging the internets, but no definitive solutions yet. Please post the update if you find something. It feels like a bug in the nVidia drivers

[jrnewell]

I had a similar issue where it would only work with HDMI and not HDMI + DVI.  Enabling CSM in the bios fixed it for me.

[anibalin]

I had a similar issue where it would only work with HDMI and not HDMI + DVI.  Enabling CSM in the bios fixed it for me.

Unbelievable. Enabling CSM did the trick. Thanks man.