XFX RX6800 XT fan not spinning up

Hi

I used this system to do quite a bit of rendering on Blender, I remember in the beginning, there was quite a loud fan howling sound when I was doing the heavy lifting during render, don't seem to hear it any more. Fan still spins on low speed throughout, doesn't appear to vary according to load.

Any way for me to find out why?

HP z640 with xeon e5 2680v4
RX 6800XT
running 13.5.1 and opencore with the bootflag agdpmod=pikera

Thanks!