PWM Fan Advice

Whiffle

Whiffle

Whiffle

Associate
Joined
27 Jul 2009
Posts
386
Hello,

I was thinking of replacing my current 3-pin case fans with some 4-pin versions.

The fans are going in a server that sits idle for most of the time, so the case fans do not need to be running full pelt all the time.

I currently have a 140mm fan at the front and a 120mm at the back.

I have never bought a PWM fan and have a few initial questions:

1. My motherboard has a 4-pin header on it. Is it better to run the two case fans off the CPU header or the motherboard header?

2. I have looked in my mobo manual and it says that the CPU header has the following pins (1 Ground, 2 +12v, 3 Sense, 4 Speed Control). The motherboard header, however, is slightly different (1 Ground, 2 Speed Control, 3 Sense, 3 NC). Why the difference? I would have expected the pins to be the same on both.

3. Arctic PWM fans seem to offer something called PST technology, which seems to be the ability to daisy-chain the fans. How does this work and is it worth going for this brand, just for this?

Thanks
 
Any reason for the 4pin requirement?

Could you not go with a fan controller? Something small and simple like the aquaero chips and fan boards? All pretty slim and easy to hide and you get software to control fan curves in your case dependant on many (and I mean a lot!) of variables?

If you're set on 4pin PWM, know that not all mobo's support 4 pin, 99% have a 4 pin for the CPU fan, but the rest are 3 pin and even then, can be speed set in the bios.
 
Your CPU header will work with PWM fans, the motherboard header however only supports voltage control, something which PWM are not great with.

You can of course use a PWM splitter to power and control multiple PWM fans.
 
Tealc said:
Your CPU header will work with PWM fans, the motherboard header however only supports voltage control, something which PWM are not great with.
Click to expand...

So the four pin header on my motherboard is not a true PWM controller like the CPU one (that would explain the difference in the pins)?

Other than the CPU header, the motherboard has a 4-pin and 3-pin header. Seems little point of them having provided both in the circumstances - seems a bit cheeky.

I guess that the CPU temperature is probably a good indicator of fan-case speed in any event - as a very general rule, I would expect temperature within a case to largely follow CPU activity.
 
As suggested, use a splitter to connect them all to the CPU header.

Only one of the splitter's heads will report a RPM back to the motherboard though - make sure this is the CPU fan's connection.
 
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