Quieten CPU Fan

I've got a bit of an issue with Desktop #2 (in my sig) - I built it to be a quiet machine, and accordingly bought some 1200rpm slipstream fans for the case.

Problem is, it's still making a right old racket, and I'm pretty confident that it's the CPU fan - stock AM2+ heatsink. The motherboard's automatic function doesn't seem to work very well - it's spinning far more quickly than it needs to as far as I can gather, because even when I've dropped the RPM manually with Speedfan and got Prime95 going the CPU still refuses to get hot. Google seems to confirm that the motherboard isn't great at getting the speed right.

So I've got myself some molex adapters for the case fans, so they aren't plugged into the motherboard any more, but I'm not sure what to do with the stock fan. If I put the molex adapter on them I'm guessing it'll spin right up to some crazy speed... what do you reckon is the best thing to do?

I'm not averse to buying a replacement heatsink, if it's easy to fit, but obviously if I can make the old one work then that would be better. And even if I do buy a third-party heatsink, I'll need to be careful - if it runs off PWM/voltage from the motherboard it'll be running at very high speed all the time.

You could use a hardware fan controller to resolve that.

These can be lo tech and cheap:

http://www.scan.co.uk/Products/Zalma...Fan-controller

Or more complex, with temp sensors, taking over the motherboard's job of variable speed:

http://www.scan.co.uk/Products/Silve...on-LCD-Display

I use the former - it works well for me.

+1 for fanmates - very good range of adjustment available. Use it with something like HWMonitor to see the fan speeds change as you adjust the fanmate.

What would a stock AM2+ CPU cooler be like at 5V then? Fairly quiet I'd guess?

I'm not too sure with the BIOS but surely you can set the fan to spin up at some ridiculously high temperature and then that would mean it'll never actually spin up the a fast RPM as it'll never reach the "ridiculously high temperature" E.g. set it to 20% normal or something and then 50% when it's 60 degrees? I've never used a Gigabyte board's BIOS though so I'm not sure how it works there with their fan settings so ignore me if this is useless.

I know for sure that the cooler would definitely be quiet though, I have a Zalman Fanmate in my siblings pc and I use it to control their 8800GS (2 pin fan connector) and it works wonders!

I doubt it, or I would've tried it already - there's just pwm/voltage/off IIRC. The only thing I've got set up is a warning at 70C I think - and this is spinning up at 30.

I'll probably give the fanmate a go then

I think I'll try the same. The CPU is constantly folding, yet the temperature is 35 degrees according to CoreTemp, and the fan whines at 2800-3200RPM - awful racket. Thing is, if my CPU fan is 4-pin (and I don't know whether it is, stock AMD fan), the simple fan-mate won't work, since it's 3-pin? Or will it?

Another option is a fan resistor cable which can undervolt it to 5V or 7V. Scan has the 5V version while QuietPC has both 5V and 7V.

http://www.scan.co.uk/Products/Zalma...r-3-pin-Fan%29
http://www.quietpc.com/gb-en-gbp/pro...ries/resistors