high GPU memory clock on RX 570 and dual displays

so, I got my mackintosh up and running with Catalina and OpenCore, so far everything I tried seems to work (horay!). However, there is one annoyance:

The GPU fans spin up sporadically (audible) at idle. Usually the RX 570 should shut off the fan at idle (2D mode, desktop) which it does under OS X with one monitor attached. In this case, the GPU clocks down to 300 MHz (core clock and memory clock) and consumes very little power.

Once I attach a secondary display (an identical display mind you), the memory clocks go up to maximum (1750 MHz) which causes a higher power consumption, a hotter card and results in spinning fans.

The strange thing is, once I boot up into windows, with the same configuration, the card stays at 300 MHz memory clock and stays cool and silent.

Is there a way to fix this?

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My configuration:

• Intel i5 10500
• AsRock Z490 ITX/ac with a Broadcom Wifi card
• Sapphire RX 570 Pulse ITX