AC Freezer Question: PWM Control

BillytheImpaler · 6 Dec 2006 at 16:23

I'm looking to upgrade a friend's CPU cooler becasue her current one is far too noisy when the motherboard spools it up into "hot" mode. It's a skt754 3200+ with the stock cooler. I'd like to install an Arctic Freezer 64 Pro becasue of that cooler's high performance to cost ratio. However, I'm concerned about the PWM speed control that that cooler uses. Her mobo does not have PWM control, it only has the old-style 3-pin fan header for the CPU. How can I get the new-style fan to work on the old-style header? Can it be done without sacrificing low-speed operation when temps are low?

Big.Wayne · 6 Dec 2006 at 17:16

BillytheImpaler said:
I'm concerned about the PWM speed control that that cooler uses

I just bought one of these, what is this 'new' feature then? :confused:

BillytheImpaler · 6 Dec 2006 at 17:24

Big.Wayne said:
I just bought one of these, what is this 'new' feature then?

If by "new feature" you mean PWM speed control...

It's a method of speed control. The old style would change the speed of fans by varying the voltage output from the header. This is a bit of a sloppy way of doing it as you can't get good speed control that way. It also limits how low you can go in terms of speed. For instance the highest speed is when output is 12V. In "quiet" mode where the fan does not need to be spooled up all the way it might drop the voltage down to 7V. You could not drop the voltage to, let's say, 2V becasue the fan wouldn't spin at all.

PWM is Pulse Width Modulation. Instead of lowering the voltage to less than 12v to go slower it turns on and off the 12V supply quickly. The longer you leave the power on, the faster it goes until it peaks at always-on. the less frequency or duration you leave the power on the slower it will go. You can achieve almost any speed lower than the fan's maximum using this method.

Snapshot · 6 Dec 2006 at 17:46

The four-pin connector fits the three-pin header on the mobo and I think you can still use voltage control.

Big.Wayne · 6 Dec 2006 at 17:52

BillytheImpaler said:
If by "new feature" you mean PWM speed control...

Hi BillytheImpaler,

Yeah by new I mean that it's not normally on these coolers, I bought a Freezer-64-Pro last week (normal box) and a Freezer-7-Pro today but its got a sticker on it saying 'NEW PWM Fan Control'

Never used one of these ARCTIC Coolers before so wasn't even aware that it was speed adjusted!

Thanks for the PWM explanation . . . :cool:

BillytheImpaler · 6 Dec 2006 at 18:58

Can somebody test or 100% confirm that it will work by plugging the 4-pin plug into the 3-pin header? Which end should hang off? I'm lookin' at you Snapshot.

Any time Mr. Wayne.

Snapshot · 6 Dec 2006 at 19:54

The connectors are keyed so there's problem working out which way it fits - the PWM pin will hang off. I was about to say I can't test this but I think I can if I put a 3-pin fan extension lead between the Freezer 7 Pro fan and the mobo. I'll report back in a bit.

Cyber-Mav · 6 Dec 2006 at 20:29

pwm is risky by turning something on and off thousands of times a minute you could either blow it up or worse.

BillytheImpaler · 6 Dec 2006 at 20:33

Cyber-Mav said:
pwm is risky by turning something on and off thousands of times a minute you could either blow it up or worse.

Blow the fan up? PWM is used in motor speed controllers in industry the world 'round. I don't get it. :confused:

Big.Wayne · 6 Dec 2006 at 20:39

NEW PWM Fan Control

4-pin Connector?

BillytheImpaler · 6 Dec 2006 at 20:47

AFAIK, Wayne, the AC Freezer's fan has always been PWM controlled. Methinks when they say "new" they mean it's the new hotness style, not the old and busted 3-pin design.

Snapshot · 6 Dec 2006 at 20:50

Right, I'm pleased to report that using voltage control on a Freezer 7 Pro worked very well on my test rig. The rig is Intel 820, GA945P-S3, 2GB DDR2/400, X1300 Pro. I stuck a 3-wire extension lead between fan lead and mobo header and set the BIOS to voltage control. The fan was off until the CPU temp reached 24C when it came on at 400rpm and rose gradually until it stabilised at 34C and 570rpm. This was in the BIOS so I now started XP and ran a few apps, ending up with Orthos. The temp and fan speeds went 36C / 700rpm, 40C / 1150rpm, 42C / 1300rpm which was the peak under Orthos with both cores at 100% for 5 min. Ambient temp was 18C.

Hope this helps.

Jonathan

BillytheImpaler · 6 Dec 2006 at 20:52

Great, it looks like this cooler will work for me. Thanks a bunch, Jon.

Big.Wayne · 6 Dec 2006 at 20:53

BillytheImpaler said:
Methinks when they say "new" they mean it's the new hotness style, not the old and busted 3-pin design.

ok I'm confused

Basically how does this connect, I thought I would just plug it in, but the CPU Fan power header is three pin?

Also I have always used the mobo (Q-Fan etc) to control the CPU fan, how does this PWM thing interact with that?

[edit]

Snapshot said:
I stuck a 3-wire extension lead between fan lead and mobo header and set the BIOS to voltage control.

Still confused? now your telling me I can't just plug this in? I need to buy a 3rd party adapter?

BillytheImpaler · 6 Dec 2006 at 20:57

As demonstrated by Snapshot above the fan will attach with one socket hanging off the end. It will behave just like a regular 3-pin fan would. You won't have PWM control though becasue your mobo doesn't support it. What Snapshot did to test if it would work by voltage control (as a 3-pin fan does) was stell his motherboard not to use PWM control but to use voltage control instead. It did and it made me happy.

EDIT: He did not use a 3rd party adapter. He just plugged it in using an extension cable to make testing easier. One pin will hang off the end of the header.

Care to take some photos to make the explanation easier, Snapshot?

Snapshot · 6 Dec 2006 at 21:02

I used a 3-wire lead because both fan and mobo are 4-wire so I was separating them to emulate the setup Billy was talking about. The connectors are designed so you can connect any combination of 3- and 4-pin. You can only use PWM if both fan and mobo are 4-pin, otherwise use voltage. I hope this clears things up.

Jonathan

Snapshot · 6 Dec 2006 at 21:04

I can do some photo's if Wayne's still confused but it won't be until tomorrow.

Big.Wayne · 6 Dec 2006 at 21:15

BillytheImpaler said:
You won't have PWM control though becasue your mobo doesn't support it.

How do you know what mobo I am using it on?

Snapshot said:
I used a 3-wire lead because both fan and mobo are 4-wire so I was separating them to emulate the setup Billy was talking about.

Ok, I didn't take my 'new' mobo out the box yet and look, but I never saw a 4-pin fan header before? What mobo you using?

BillytheImpaler · 6 Dec 2006 at 21:17

Big.Wayne said:
How do you know what mobo I am using it on?

Ah, I assumed that since we were having this discussion your mobo has a 3-pin CPU fan header. If it's a new mobo it'll probably have a 4-pin header.

Big.Wayne · 6 Dec 2006 at 21:26

BillytheImpaler said:
If it's a new mobo it'll probably have a 4-pin header.

Cool, how long have 4-pin fan-headers/fans been around?

What's the extra pin do then?

2-pin = Basic Fan Power (although its still mounted in a 3-pin casing)

3-pin = Basic Fan Power + RPM reading

4-pin = ???

AC Freezer Question: PWM Control

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