Let it for more than 2 -3 minutes. Try 4 instances all showing up with maximum anti-aliasing + anisotropic filtering and all the effects on, all side by side or something. 15 minutes or so should heat it enough.
Consider it might not be your graphics card that is the problem, but your CPU fan or such since you said it gets noticeably louder normally. RTHDRIBL will not stress your CPU in the way a game could.
Edit: lol cmm![]()