@yabusa,
After a little experimentation on my Z390 Designare with two AMD GPUs (RX580 in slot 1 and RX 5700 XT in slot 2), I was able to disable the RX 5700 XT (slot 2) with the attached SSDT.
Filename:
SSDT-Disable-AMD-GPU-Slot-2.aml
Please give this a try.
CAUTION: Please monitor backplate temperature of the 'disabled' GPU with a temperature probe or thermal imaging probe. The card may remain powered although a driver won't attach to it. Periodically check to see if the disabled GPU's fans spin up to maintain a safe temperature.
Slot 1 and slot 2 versions of this SSDT are also posted here:
I have this system: MB: Gigabyte Z490 Vision G CPU: Intel Core i5-1500 6 Core RAM: DDR4 64 GB 3200 GHz Graphics: Radeon RX 570 - 8 GB DDR5 NVMe M.2 Samsung SSD 970 EVO (1 TB) + Crucial SSD P2 - 2 TB (secondary) WiFi+Bluethoot: MQUPIN BCM94360CD (recognized natively by Big Sur and previous)...
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