15.5 AMD Radeon6900XT - behaving like there's no drivers

[artaxerxes131]

I have an AMD Radeon 6900XT that I've just installed into my 7,1. I am running into issues that I was not anticipating.
According to the documentation I can find from Apple(1,2), this should work without issues. It's the right card with the right Device ID to be supported (0x73bf), but the Mac is behaving like it does when it has an unsupported card.

Here's what I'm running into:

• No ability to control or adjust display resolution
• Only one monitor detected, no matter what's plugged in
• If the display that's plugged in on boot is disconnected, it does not reconnect.

In fact, it's behaving exactly like MacOS did back in the 10.13 days when I had an NVIDIA card in with no driver. However, as the 6900XT is, in theory, supported natively I cannot figure out what's the issue is. I have checked, and can confirm the following are not the problem:

• the cables
• the monitors
• the card itself (runs fine in a Windows system, and in the Bootcamp partition)

This is looking more and more like it's a MacOS issue. I am running 15,5 and the card is seen in the system profile. Per instructions from multiple forums I removed the stock 580X, and am using the Display Ports on the back of the GPU.
I'm at a loss - anyone have any ideas?

System Report Output:

AMD Radeon RX 6900 XT:

Chipset Model: AMD Radeon RX 6900 XT
Type: GPU
Bus: PCIe
Slot: Slot-1
PCIe Lane Width: x16
VRAM (Total): 16 GB
Vendor: AMD (0x1002)
Device ID: 0x73bf
Revision ID: 0x00c0
ROM Revision: BR78660.001
Metal Support: Metal 3
Displays:
ASUS PB287Q:
Resolution: 5120 x 2880 (5K/UHD+ - Ultra High Definition Plus)
UI Looks like: 2560 x 1440 @ 30.00Hz
Framebuffer Depth: 30-Bit Color (ARGB2101010)
Main Display: Yes
Mirror: Off
Online: Yes
Rotation: Supported
Connection Type: Thunderbolt/DisplayPort

 

[artaxerxes131]

And, unsurprisingly, there are other threads of folks who have this card running perfectly fine in their systems (see one link below)

I have done a reinstall of MacOS 15.5, which has not resolved the issue.

https://forums.macrumors.com/threads/mac-pro-7-1-and-amd-radeon-rx-6900xt.2309594/