Why do boards come with a mixture of pwm and voltage controlled fan headers?

ZodaEX

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I'm curious as to why modern motherboards still ship with a combination of both 3-pin voltage controlled fan headers, as well as a 4-pin PWM styled one.
Why doesn't the industry just settle on deciding to use either 3-pin or 4-pin? Why both?
 

Nobu

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I'm curious as to why modern motherboards still ship with a combination of both 3-pin voltage controlled fan headers, as well as a 4-pin PWM styled one.
Why doesn't the industry just settle on deciding to use either 3-pin or 4-pin? Why both?
PWM controllers can only handle so many fans before the signal is degraded, and adding some voltage controlled headers is a cheap way to add one or two.
 

Smoblikat

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They make 3 and 4 pin fans still, so there is a need to be able to control both types.
 

ZodaEX

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They make 3 and 4 pin fans still, so there is a need to be able to control both types.

Actually, a 4-pin fan is backwards compatible with a 3-pin fan header.
So why aren't all modern fan headers just made to the 4-pin spec?
 

Nobu

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Actually, a 4-pin fan is backwards compatible with a 3-pin fan header.
So why aren't all modern fan headers just made to the 4-pin spec?
Most will accommodate a 4p fan cable. Why "most" and not "all", I don't know. :/

Space is probably the main reason in many cases
 

ZodaEX

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Most will accommodate a 4p fan cable. Why "most" and not "all", I don't know. :/

It's because sometimes they'll be a capacitor in the way, blocking a 4-pin lead from having enough clearance to be plugged in. However you can easily get around this issue with a 3-pin extension cable.
 

Smoblikat

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Actually, a 4-pin fan is backwards compatible with a 3-pin fan header.
So why aren't all modern fan headers just made to the 4-pin spec?

I guess ive never tried (or dont remember trying) but wouldnt it just run at full speed if you plug the 4 pin fan into the 3 pin header? I assume it would be expecting a PWM signal and not receive any, so it either runs flat out or not at all.

Ive heard that some 4 pin headers also support voltage ramping for 3 pin fans (depends on the board), so assuming your 4 pin header is also capable of controlling 3 pin fans, then you would be right in assuming settling on one standard is better. But I dont believe a 4 pin header has to be able to control 3 pin fans, so dedicated 3 pin headers would be needed for compatibility with those fans.
 

ZodaEX

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Why did the industry start using 4-pin fan headers to begin with? They seem to more or less serve the same function as 3-pin.
 

Nobu

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Why did the industry start using 4-pin fan headers to begin with? They seem to more or less serve the same function as 3-pin.
Need a power, ground, PWM, and sense (rpm) pin. You could theoretically combine two of the pins, but it adds complexity where one extra pin is sufficient.
 

ZodaEX

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Need a power, ground, PWM, and sense (rpm) pin. You could theoretically combine two of the pins, but it adds complexity where one extra pin is sufficient.

The 4-pin ones do need a pwm pin, but the 3-pin ones didn't. So why did the industry start using the 4-pin style headers on some motherboards? Why did they "fix" what wasn't broken? It just seems arbitrary to change the headers for no reason.
 

Smoblikat

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PWM fans have a few advantages, such as lower minimum speed, and being guaranteed to not stall regardless of what speed you tell them to run at.

Thats true, I didnt think about that. Ive definitely undervolted 3 pin fans to the point they dont spin.
 

ZodaEX

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So if it's a cost issue, why don't the super high end motherboards just have all 4-pin headers? I feel like there must be an engineering reason for using voltage control for some of the fans but I just can't think of what it would be.
 

Dan_D

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Actually, a 4-pin fan is backwards compatible with a 3-pin fan header.
So why aren't all modern fan headers just made to the 4-pin spec?
I can't recall the last time I saw a 3-pin fan header on any modern motherboard. The vast majority are 4-pin.
 

pendragon1

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As someone who has been reviewing boards for 15 years, I can tell you very few of them have 3-pin headers anymore. Like I said, I can't recall the last time I saw one.
im sure youve touched a tonne more than me. i think they started disappearing around the intel 7000 series time. they were still on boards from 5-6 years ago for 6000 series intel systems ive worked on recently.
 

Dan_D

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im sure youve touched a tonne more than me. i think they started disappearing around the intel 7000 series time. they were still on boards from 5-6 years ago for 6000 series intel systems ive worked on recently.
I think I've mostly seen 4-pin only since about the Z170 era onwards. Where I have seen 3-pin headers since then it's been on budget offerings primarily.
 

pitingres

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As someone who has been reviewing boards for 15 years, I can tell you very few of them have 3-pin headers anymore. Like I said, I can't recall the last time I saw one.

Asrock B450M Pro4-F. I got stuck with one via ebay, was sold as a regular Pro4. Bletch.
 

evhvis

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So if it's a cost issue, why don't the super high end motherboards just have all 4-pin headers? I feel like there must be an engineering reason for using voltage control for some of the fans but I just can't think of what it would be.
Are there still high end boards with 3 pin headers? My high end x570 board has 7 4-pin that control both 3 pin and 4 pin and two of those are 3 amp headers (normal is 1 amp). My mid range x570 board has 4 4-pin headers, also only 4 pin and my old mid range z270 board only has 4-pin headers as well. All my 4-pin headers can control 3 pin DC fans. The main reason for using 3-pins on a motherboard is cost savings.

The main advantages of 4-pin PWM are low RPM (300RPM on a 2200RPM fan is generally not possible on a 3-pin DC fan) and fan-stop without damaging the fans.
 

Dan_D

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So if it's a cost issue, why don't the super high end motherboards just have all 4-pin headers? I feel like there must be an engineering reason for using voltage control for some of the fans but I just can't think of what it would be.
Show me a single super high end motherboard that uses anything but 4-pin fan headers. Try and even find one made in the last five years that has a single 3-pin fan header on it. I'll wait.

Are there still high end boards with 3 pin headers?
No, there aren't.
 
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JSHamlet234

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I didn't know this was a thing. I've bought 6 motherboard in the last 6 years, since I got back into this hobby, and I haven't seen a single 3-pin header in all that time. The boards ranged from cheap to barely mid-range.
 

mwarps

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I haven't seen a 3-pin fan header in a very long time. Haswell era?
 

ZodaEX

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I just bought a new motherboard and it came with all 4+pin fan headers. I guess the industry read my mind. :)
 

doyll

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Just because all fan headers are 4-pin doesn't mean they are PWM.
I've seen motherboards saying they have "PWM fan headers" that their 4-pin fan headers have pulsed 12v (PWM power on pin-2 and nothing on pin-1. Some are variable voltage on pin-2 so not' PWM' any way you look at it..
Some 4-pin 'PWM' fan header pin-out is:
pin-1 = unused​
pin-2 = PWM (pulsed 12v)​
pin-3 = rpm signal​
pin-4 = ground​

Real 'PWM' fan header pinout is:
pin-1 = PWM control​
pin-2 = 12v​
pin-3 = rpm signal​
pin-4 = ground​
 
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