I recently installed an Asus 4850 into my new pc build after experiencing the dreaded nvlddmkm errors in Vista 64-bit with my 8800GT. I love the 4850 so far but heat is definitely an issue. I've installed the Asus Smart Doctor and set the to manual and left it at 50% all the time. It keeps the temp around 50°C at idle but the problem I have is the fan automatically cranks up to full 100% whenever temps reach exactly 75°C. The fan will remain at full speed like this until I open Smart Doctor, open fan settings, hit ok (without even changing anything) and the 50% fan speed setting goes back to normal. It's very strange, I can't figure out what software or which setting is causing the fan to turn up at the 75°C mark. Personally, I think that is fine for Video Cards, which is why I want the fan to remain at 50% speed all the time. Any ideas? This is a brand new build and the only video card related software I have installed are Asus Catalyst control center with Overdrive (all default settings), Asus GamerOSD (has nothing to do with the fan, it's for recording videos in games), and the Asus Smart Doctor tool which, like I said, I have set to manual fan speed of 50%. Please help, the noise level of the fan at 100% is absolutely obnoxious and I cannot figure out why it is kicking in at 75°C. Thanks in advance.

Thanks for the quick response, but I think you need to do a little more research. Yes, 75°C is not ideal, but it is certainly not anywhere near meltdown. People never give these cards enough credit, they can handle a lot more heat than you think, that's how they were designed. Also, my question wasn't whether or not 75°C is a bad temp, I just want to know which setting is causing it to crank the fan up to 100% at this specific temperature and how I can disable that or edit the value to be higher, like 85°C.

its a bit hot get ati tool tray to edit fan speeds
latest can be found here

http://forums.guru3d.com/showthread.php?t=270486
http://cid-a50350ea7a969f0c.skydri [...] tsetup.exe

depending on the size of the heatsink, there is a certain temperature in which the amount of energy being dissipated becomes a runaway train, and no matter how much air passes over it, it will continue to rise in temperature.

Asus saw 75C as the uh oh moment to prevent overheating the fan has to kick on right then. Upgrade your heatsink and fan to something much larger and more efficient voiding the warranty anyways, and all will be well.

I am absolutely positive that I do not have it on auto or smart cooling, that is what is confusing me about the fan going to 100% when I hit 75C. I have tried those before and didn't like the "revving" of the fan every time I played a game so I put it on 50% manual.

Thanks for the replies all but my question is not if these are good temps, if I should I buy a cooler, or anything like that. I simply want to know why the fan increases to 100% at 75C when I specifically set Smart Doctor to manually stay at 50%.

Could you please tell me which software you have installed for your card? I would be curious to know if you're using similar utilities such as Catalyst or Smart Doctor so we might be able to figure out where this setting is. When your fan cranks to 100%, does it ever come back down on its own? Mine will stay full bore until I go into the Smart Doctor settings and hit ok again, even after the game is long done.

Even though you set it to manual, your settings are not sufficient (to the card) at keeping it cool. So it is auto turning up the fan speed to keep itself cool. The card can run at 75c without serious issues in the short term, but it is not designed to run that hot all the time. That's just the way it is.

Thanks for the info, that is exactly what happens to me too. Weird. I might try uninstalling Smart Doctor and see if the 75C mark is some kind of safety net. I'll post a reply if I figure it out.

Well I uninstalled smart doc and then re-installed the latest version 5.24 (was running 5.20) and the fan rev at 75C no longer happens. Just to be safe, I'm going to use the Smart Cooling option so the fan incrementally spins faster, which is much nicer than the instant blast to 100% like before. We'll see how this works out...