4 pin quiet fans?

Firetech · Post by **Firetech** » Mon Jun 12, 2006 9:17 pm

With Intel and now AMD (with AM2) having 4pin MB fan header (not molex) connections, have there been any sightings of 'quiet' 4 pin fans?

oDii · Post by **oDii** » Mon Jun 12, 2006 10:26 pm

And while we're at it, what is the fourth connector actually used for? People have tried to tell me PWM, but fans are perfectly capable of that without modification/extra wires.

ultraboy · Post by **ultraboy** » Tue Jun 13, 2006 5:17 am

I've been searching for this as well - to use as VGA fan which has an on board 4-pin connector.

It seems only JMC has it available in after market in 80, 90 and 120 mm. sizes. And according to frank in this thread, it performs quite well.

Btw, oDii, that linked thread answers your question too.

dinofx · Post by **dinofx** » Tue Jun 13, 2006 5:40 am

The JMC fans are pretty quiet. I can't really hear my 120mm until it reaches about 1100 RPMs. I think it goes up to about 2700 rpms. My only complaint is the size of the dead spot in the middle of the fan. Compared to the really noisy, silver, SilenX fans, the motor in the center of the JMC fan is huge. But maybe this is normal and SilenX is the exception. Another minor issue is that the JMC fan will stop at below 20% duty cycle. The Intel specification does not allow for this, but some buyers may appreciate being able to stop the fan (even though it is probably still drawing current)

The 4th wire is the PWM signal at around 25KHz. The duty cycle varries from 0 to 100%, and the signal can be pulled up to 5.25 volts. I don't get the second comment. How can fans already do PWM without a pulse signal?

Shuttle computers come with 92x25mm, 70x15mm, and 60x15mm PWM fans. All of them seem to be OK. I think one Shuttle dealer in the UK sold these fans individually, but I haven't been able to find the site.

CL · Post by CL » Tue Jun 13, 2006 12:59 pm

I thought that the extra pin was a ground pin. That's what I gathered from my motherboard spec, Intel D945GNT, page 61.

frankgehry · Post by **frankgehry** » Tue Jun 13, 2006 3:46 pm

The 4 pins are:

1. pwm
2. 12v
3. ground
4. tach

TomZ · Post by **TomZ** » Tue Jun 13, 2006 6:46 pm

I've got some JMC 80mms here - they are pretty quiet at low RPMs and pretty loud at high RPMs.

One advantage of the 4-wire fans is they allow greater range of control, so they can run at pretty low RPMs. Also, they PWM at 20-30kHz, outside of the audible range, so the PWM should not add any additional noise (no clicking, humming, etc.).