Dual display issue on Optiplex 9020m / FrameBuffer Patching Confusion !

[bisk]

Aloha all,

 

I am having a very interesting problem with dual displays on my Dell Optiplex 9020m. This is a Haswell tiny form factor desktop running Big Sur 11.7.4. I could easily update to Monterey but I'd like to solve this problem first.

 

This is a Core-i7 system so it's the Intel HD4600 iGPU and I;m running with OpenCore 0.88.

 

Everything works perfectly, SpeedStep, Sleep/Wake, USB ports, WiFi, BlueTooth, you name it - all except one thing.

 

If I try to boot with 2 displays attached, I end up frozen with 2 blank displays. But here's the strange thing.

 

If I boot up with only the right display attached and then connect a 2nd display to the left video port, the system blacks out momentarily in recognition of the change but only the original right display comes back. The left display remains black but is in active signal mode. There is no additional active FrameBuffer, just the one associated with the original booted display.

 

If I boot up with only the left display attached and then connect a 2nd display to the right video port, the 2nd display pops right up and both displays perform perfectly and all is well even through any number of sleep/wakes.

 

This system has dual Digital Video ports and when each display is functioning, the left is on FrameBuffer@1 and the right is on FrameBuffer@2.

 

If I compare this to another very similar system that I've recently built, Lenovo ThinkCenter M83, I have no issues with dual displays at all. However, there is a difference, the displays connect to FrameBuffer@0 and FrameBuffer@1 on this Lenovo model.

 

Both of these systems are defined as Macmini7,1, both connect to the same exact displays and I've used DV->HDMI video adapters on both as well.

 

I also have a few questions as I am still not that experienced with FrameBuffer patching.

 

1. Is the port-number attribute that we see in FrameBuffers what equates to busid ?

2. If the busid is set to 0 for a particular FrameBuffer should that FrameBuffer drop out of the Registry ?

3. What attribute equates to the pipe ? 

AAPL,DisplayPipe is either 01000000 or ffff0000 depending on whether connected to a display or not.

 

So far, in my patching experiments, I only see the connection type changing, never the port-number.

That's why I ask if port-number=busid. I never drop a FrameBuffer or affect port-number no matter how much I play with patching in DeviceProperties.

 

 I've tried changing connectors individually : framebuffer-con0-busid = 0

or all at once : framebuffer-con1-alldata = 01050900 00080000 87000000

 

I see no difference in IORegistry except the connection type changing between DV and HDMI.

 

On the 9020m, I always see:

 

FrameBuffer@0 : port=5

FrameBuffer@1 : port=6

FrameBuffer@2 : port=0

 

This is exactly what I see on the Lenovo too only the displays connect to FB@0 & FB@1 instead of FB@1 & FB@2.

 

Any guidance greatly appreciated

 

 

Edited March 6, 2023 by bisk