Your fan's "issue" sounds very normal to me (I assume you mean the PCIe and PSU fan spin up more than required). You may try few things including SMC reset, stress the GPU for a few seconds (e.g. by running Luxmark), or custom make your fan profile for these 2 fans (e.g. via MacsFanControl).
Also, that particular RX480 has zero dB cooling. The fan should not spinning when the GPU is under light load.
@
h9826790 You are right! I might have overreacted a little lol. Nothing to worry about - all temps seem normal. After careful observation, when RX480 together with GT 120, PCIe and PSU went crazy at full blast like
this. SMC reset and GPU stress didn't help. The only way to stabilize the full-blown fan speed is to, without GT 120, do kext edit (as
TheITSage suggested) after SIP is enable without Kext in recovery, only then do NVRAM reset with both installed. In that way, SIP is enabled yet kext repair permission is still intact (hopefully Apple won't change it in future), and all good to go!
With GT120 tho, RX 480's performance diminishes about 10% less according to Luxmark. It works fine for day-to-day tasks, but under Luxmark stress mode running, the graphic becomes visually sluggish even on performing a simple task like mission control. Without GT 120, RX 480 rocks at full extent (16 CUs activated). However, with GT 120 attached you can get significant increase of performance from RX 480 by plugging monitor cables over to RX 480 ports after booting the screen with GT 120, but still get less luxmark score than with RX 480 alone.
Sorry to report that the only solution I found was to remove the GT120
I never had any "fans issue" here but I have a reference RX480 from Sapphire (not a Nitro).
Yah Sapphire Nitro+ triggers fan issue but not a big deal (See above). Now I got them together working well in window 10 bootcamp as well. Selection of correct drivers for GT 120, specific way to install RX 480 drivers and lots of restart are involved, it's well worth it however.
