What Makes The GPU Hotter?

I read in some post here about something which i dont quite remember but it said that when the card uses its transistors it gets hotter and it mentioned AA and HDR.

I recently added another fan to my computer and my 8600GT reaches nearly 75C (Instead of nearly 90) under load so i wanted to know which special effect makes the card hotter? Anti Aliasing or HDR?

Frankly i can live without out AA but HDR really adds to the game (Oblivion). I cant even imagine how hot my GPU will get in a DX10 game.

ha! you should see my giant fan i place near my PC to keep things cool = D
(its actually a dust ionizer)

but i have 6 fans in my PC, they're exhaust and intake fans, and all using factory made, not stock. My vc temp stay at 65-67c* at heavy load (running mostly high end game like Overlord, Neverwinter Nights 2 or BF2142 at max setting, and 55c* at idle.

Heres a small video I made for Overlord with every thing max out.

http://www.gametrailers.com/player/usermovies/79656.html