RX580 doesn't work correctly until I wake computer from sleep

[9000RPM]

I've been using High Sierra with a GT720 for over 2 years but decided to upgrade to a RX580 recently.  I also made a fresh install of Mojave 10.14.6.  The motherboard that I'm using is from the Optiplex 790 MT. 

 

The issue that I'm having is with the graphics card.  It is a RX580 from HP.  Google says it's a "Dooku" card.  It has 4 ports (3DP and 1HDMI).  I have 1 monitor connected to the DP and another connected to the HDMI. Both has signal until it boots to the login screen, then the HDMI monitor turns black.  From there, the graphics are very sluggish and with occasional artifacts. The HDMI monitor does get signal but it's just black.  I can see the monitor in the System Preference display property using the DP monitor.

 

What I'm doing now to fix this is to put the computer to sleep.  Once I hear the fans stop spinning, I can immediately wake it up and both computers will get signal.  No more choppy graphics.  I've compared the GPU benchmark scores on Geekbench between Mojave and Win10 and both score about the same, so I know the performance issue is fixed once I wake it from sleep. 

 

Attached is my clover dump. If anyone can take a look, that would be awesome. 

 

I tried injecting "Inject ATI", "Acre" for the framebuffer.  This makes the HDMI monitor work perfectly from first boot but none of the 3 DisplayPorts will get signal. 

Debug file: https://www.mediafire.com/file/4gmy8zv4eyesc3h/debug_4002.zip/file

 

[MaLd0n]

what processor?

[9000RPM]

5 minutes ago, MaLd0n said:

what processor?

i5-2500

[MaLd0n]

try with dp output

legacy mobo

[9000RPM]

21 minutes ago, MaLd0n said:

try with dp output

legacy mobo

Hi MaLd0n,

I tried with a monitor just plugged into the DisplayPort and it boots fine, no lag.  The moment I plug in another monitor, whether it's DP or HDMI, it is just a black screen until I put it to sleep and wake it.

Thanks.