Why do I get 4-wire fans?

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I have asked this before, but still have not resolved the issue.

I am looking to get a couple of 92 mm 4-wire case fans. By 4-wire, I
mean they should have a "Sence" wire which is the fan tachometer output
with two pulses per revolution and a  "Control" signal wire to control
the speed (Pulse Width Modulated).

I thought I had found some, as this one describes the fan as having a
4-wire connection.


but they seem to be fans with 2 wires that have one of the large 4-pin
plugs on them which supply power to things like IDE disks, CD-ROM drives
etc. It was not what I thought it was going to be.

Anyone know where I can get a fan that uses 4 wires to give speed
control and speed sencing?

Dave K     MCSE.

MCSE = Minefield Consultant and Solitaire Expert.

Please note my email address changes periodically to avoid spam.
It is always of the form: month-year@domain. Hitting reply will work
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Re: Why do I get 4-wire fans?

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There's usually some on here: http://www.dorothybradbury.co.uk /


Re: Why do I get 4-wire fans?

This page provides a long list of fan manufacturers which may help;



Re: Why do I get 4-wire fans?

On Sat, 22 Apr 2006 19:35:07 +0100, "Dave (from the UK)"

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Frankly it's unnecessary.  You'd be better off getting a
high quality fan (relatively no concern about failure thus
no concern about RPM), in a design that is quieter ALL the
time so it's fairly unimportant whether you could reduce RPM
during lowest power periods, because the fan is already
quieter even at the higher RPM.  For example, Panaflo.

Using high quality single speed fans a system can be quiet,
it can be more reliable because adding mechanical connectors
and sensing/control circuits on motherboards are not as
mature a technology as the fans already were.  

The 4 pin fan is useful for CPU where the
spot-thermal-density has such a large variation, but
considering the entire chassis, there is nowhere near the
same temp change and any thermal sensor will be ill equipped
to change fan speed based upon such minor changes unless you
custom design your own that is tunable to the specific temp
range the system sees.  

So, there's a large part of why we don't see more 4 pin fans
except integrated in a specific environment already where
the operating parameters were already known, the fan spec
possible by fewer variables.

Sorry that's not really help in finding them, but the entire
world does without fine, the issue of noise is only one of
adequate air passages and selection of appropriately low RPM

Re: Why do I get 4-wire fans?


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There is one situation where those fans excel. If you have
two running at half speed in a mission critical situation,
if one fails you can sense the failure and signal the
remaining fan to go to full speed.

Re: Why do I get 4-wire fans?

On Mon, 24 Apr 2006 05:47:29 -0700, houston we have a
problem wrote:

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IMO, the potential for failure is over 2X that without the
control, so even with two fans you'd still be more likely
for the mission critical device to go down.  The PWM itself
has the potential to damage the fans even before considering
the rest of it's implementation.

For them to excel, first and foremost they would have to be
available in best quality fans.  An engineer spec'ingn for a
company ordering sufficient quantity can accomplish this but
someone buying only a handfull of fans wouldn't have it so

Re: Why do I get 4-wire fans?

Apr-2006@southminster-branch-line.org.uk wrote:

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A spec defining the fans is here:


A search for "intel pwm fan" turned up this, but most of the
rest of the links returned, were for a combination heatsink plus
fan. And that is not a very cost-effective way to buy the
fan you want. This is the only one I found for sale stand-alone,
and it is listed as out of stock.

ARX 92mm 4 Pin LGA775 PWM Fan


Re: Why do I get 4-wire fans?

They're out there, I bought a couple of 12cm and one 8cm for my system.
I had to search a bit to find them, but they were available for a reasonable
cost, about $15/ea.

However, I went back to using them in 3-pin mode because my BIOS doesn't
init them very well when returning from S3 sleep-state.
So, like someone else said, why bother, IMO.  Most MBs do just fine
regulating the speeds with 3-pin fans.


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