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A Rant About PWM (in general) & Z97 MBs

Nuluvius
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This is a prime example of bad advertising:

http://forum.corsair.com/v3/showthread.php?p=710824

The headers on these latest motherboards are not PWM despite having four pins. They actually use voltage (as I am sure most of you are already aware) to control RPM instead. Most fans have a lower bound voltage tolerance on spin up of somewhere between 30%~40%

With default settings they certainly won't start up from a cold boot as the temps would not be high enough to warrant a 30%~40% ramp up. Only after some time operating would temps get high enough to signal an increase thus starting the fans.

This is a configuration issue at the end of the day. Rectified by setting the base tolerance to just enough to kick the fan off in both BIOS & any software that supersedes at the OS level.

I don't think there's nearly enough documentation on modern fan control methodology to be honest. Certainly the advertising glosses over the fact that MB headers are actually voltage regulated. There's only two true PWM signal headers on the boards; the main CPU fan header and the CPU OPT header. 

Indeed one could well plug in a splitter and daisy chain the PWM signal around their case. However doing so only gives you PWM in the context of the CPU and NOT the individual temperature sensors located around the board. So in that respect it ends up being totally pointless and even detrimental for case fans; imagine the scenario where the GPU or the chip set gets hot ahead of the CPU. Basically your context is not globally considerate.

Yes fan speed control is argued to not matter with case fans. I disagree, we have a feature-set there, why not take advantage of it. Personally I can't be bothered to use a control unit as I'd prefer for the software to do what it's been designed for therefore saving me flicking switches and groping knobs all the time.

The single biggest problem in communication is the illusion that it has taken place.

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wait even the Maximus VII hero?

uh oh

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The link you posted does not have anything to do with what you said in your post...

Also I'm very confused as to what point you are getting at here...

Motherboards that have a 4 pin PWM header will control the fan USING PWM if it is a 4 pin PWM fan.

Motherboards ram up all fan speeds to 50-100% at startup to start them going.

With AI Suite you can control what temperature sensors the fans respond to, completely independent from CPU temperature.

So what exactly are you ranting about here...?

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The link you posted does not have anything to do with what you said in your post...

 

"...The fans also do not start up themselves when the PC is turned on, which I believe is caused because Asus' Fan Xpert from Ai Suite II doesn't ramp them up full speed on boot...."

 

Please enlighten me as to how not?

The single biggest problem in communication is the illusion that it has taken place.

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"...The fans also do not start up themselves when the PC is turned on, which I believe is caused because Asus' Fan Xpert from Ai Suite II doesn't ramp them up full speed on boot...."

 

Please enlighten me as to how not?

Oh thats what your rant is about?

It is probably that you got some defective fans with the case. A lot of the cheaper Corsair fans that come stock (the grey ones) have low RPM issues.

I had the same problem with my H100i stock fans. Just replace them with some of the proper corsair fans, or something even better like a noctua. This is not a problem with AI Suite.

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The link you posted does not have anything to do with what you said in your post...

Also I'm very confuse as to what point you are getting at here...

Motherboards that have a 4 pin PWM header will control the fan USING PWM if it is a 4 pin PWM fan.

Motherboards ram up all fan speeds to 50-100% at startup to start them going.

With AI Suite you can control what temperature sensors the fans respond to, completely independent from CPU temperature.

So what exactly are you ranting about here...?

 

Motherboards with 4 pin headers DO NOT use PWM. Read the manual, that fourth pin is a feedback signal in pin. The only exception to this is the CPU and OPT header.

The single biggest problem in communication is the illusion that it has taken place.

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Motherboards with 4 pin headers DO NOT use PWM. Read the manual, that fourth pin is a feedback signal in pin. The only exception to this is the CPU and OPT header.

What motherboard are you talking about here...?

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Oh thats what your rant is about?

It is probably that you got some defective fans with the case. A lot of the cheaper Corsair fans that come stock (the grey ones) have low RPM issues.

I had the same problem with my H100i stock fans. Just replace them with some of the proper corsair fans, or something even better like a noctua. This is not a problem with AI Suite.

 

Defective, probably that was his second point, not so concerned with that at all.

 

That is exactly my point it's not a problem with the software layers at all. BIOS is first, it has the profile for boot control, which is then superseded by the OS level software i.e. the AI Suite. The problem is unclear advertising and the obscurity around 3 pin/4 pin headers, fans and connector differentials.

The single biggest problem in communication is the illusion that it has taken place.

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What motherboard are you talking about here...?

 

For reference that's going to be all of the current Z97 series - just look at something like the Asus Z97 - A for example. Page 38 of the manual details the header pinouts. This additionally applied irrespective of make (they are basically the same PCB core standard).

The single biggest problem in communication is the illusion that it has taken place.

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For reference that's going to be all of the current Z97 series - just look at something like the Asus Z97 - A for example. Page 38 of the manual details the header pinouts. This additionally applied irrespective of make (they are basically the same PCB core standard).

What SPECIFIC motherboard are you talking about? Give a link.

I looked up the manual to a Z97 ASUS motherboard and it only goes to page 28.

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What SPECIFIC motherboard are you talking about? Give a link.

I looked up the manual to a Z97 ASUS motherboard and it only goes to page 28.

 

 

 

"..Asus Z97 - A..."

 

http://dlcdnet.asus.com/pub/ASUS/mb/LGA1150/Z97-A/E9060_Z97-A.pdf

The single biggest problem in communication is the illusion that it has taken place.

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Yeah it says the 4th pin is 5v.

Whats wrong with that? This is how PWM works...

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Yeah it says the 4th pin is 5v.

Whats wrong with that? This is how PWM works...

 

No it is not. It is voltage control.

The single biggest problem in communication is the illusion that it has taken place.

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No it is not. It is voltage control.

Voltage control uses only 3 pins. Maybe you should learn about how PWM works...

 

Wikipedia:

 

Pulse-width modulation[edit]

Pulse-width modulation (PWM) is a common method of controlling computer fans. A PWM-capable fan is usually connected to a 4-pin connector (pinout: Ground, +12 V, sense, control). The sense pin is used to relay the rotation speed of the fan and the control pin is an open-drain or open-collector output, which requires a pull-up to 5 V or 3.3 V in the fan. Unlike linear voltage regulation, where the fan voltage is proportional to the speed, the fan is driven with a constant supply voltage; the speed control is performed by the fan based on the control signal.

The control signal is a square wave operating at 25 kHz, with the duty cycle determining the fan speed. Typically a fan can be driven between about 30% and 100% of the rated fan speed, using a signal with up to 100% duty cycle. The exact speed behavior (linear, off until a threshold value, or a minimum speed until a threshold) at low control levels is manufacturer dependent.[3]

Many motherboards feature firmware and software that regulates these fans based on processor and computer case temperatures.

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Voltage control uses only 3 pins. Maybe you should learn about how PWM works...

 

Wikipedia:

 

Pulse-width modulation[edit]

Pulse-width modulation (PWM) is a common method of controlling computer fans. A PWM-capable fan is usually connected to a 4-pin connector (pinout: Ground, +12 V, sense, control). The sense pin is used to relay the rotation speed of the fan and the control pin is an open-drain or open-collector output, which requires a pull-up to 5 V or 3.3 V in the fan. Unlike linear voltage regulation, where the fan voltage is proportional to the speed, the fan is driven with a constant supply voltage; the speed control is performed by the fan based on the control signal.

The control signal is a square wave operating at 25 kHz, with the duty cycle determining the fan speed. Typically a fan can be driven between about 30% and 100% of the rated fan speed, using a signal with up to 100% duty cycle. The exact speed behavior (linear, off until a threshold value, or a minimum speed until a threshold) at low control levels is manufacturer dependent.[3]

Many motherboards feature firmware and software that regulates these fans based on processor and computer case temperatures.

 

Yes we can all use wikipedia, thank you.

 

Those headers are not PWM. They are voltage controlled. They use voltage to ramp the RPM and the PWM IN signal pin to detect that RPM.

The single biggest problem in communication is the illusion that it has taken place.

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Yes we can all use wikipedia, thank you.

 

Those headers are not PWM. They are voltage controlled. They use voltage to ramp the RPM and the PWM IN signal pin to detect that RPM.

No that is not how fan headers work. The firs two pins are GROUND and +12v.(this is not always 12v. in can be regulated by the motherboard to less than that, which is called voltage control) The third pin is the tachometer that monitors the RPM. The fourth pin is the 5v @ 25000Hz that the motherboard uses to control the fan by varying the pulse length of the 25kHz. This is not voltage control, it is PWM.

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No that is not how fan headers work. The firs two pins are GROUND and +12v.(this is not always 12v. in can be regulated by the motherboard to less than that, which is called voltage control) The third pin is the tachometer that monitors the RPM. The fourth pin is the 5v @ 25000Hz that the motherboard uses to control the fan by varying the pulse length of the 25kHz. This is not voltage control, it is PWM.

 

That's fine. However those headers are not PWM. They are voltage control. Mine is not the first posting to highlight this.

The single biggest problem in communication is the illusion that it has taken place.

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That's fine. However those headers are not PWM. They are voltage control. Mine is not the first posting to highlight this.

They only do voltage control when it is a 3 pin fan. It also works for PWM. Show me proof that it is not PWM by putting a voltmeter on the +12v and GND. If it stays at 12v then it is PWM.

Your previous post is also incorrect. You cannot send a rpm signal through the 4th pin because ALL FANS ARE THE SAME. the industry standard is that the 3rd pin in the rpm, and 4th pin is the +5v or +3.3v. I don't think you understand how voltage works...

I can assure you 100% that the 4 pin fan headers on all motherboards are PWM enabled.

 

Also I have looked for more topics about you 'fake' 4 pin headers, and it is not true. There is proof that JJ used Fan Xpert 2 to turn down chassis fans to 20%, obviously only possible with PWM. Also I have found this:

 

"The Asus web site is just starting to list manuals for their Z97 range, and have looked at them... the chassis fan headers still seem to be of the 'fake' variety since the connectors are labelled in exactly the same way as the Z87 boards (Z97 PRO and ROG Maximus VII). It is possible that this is a mistake, and the connector diagram from the Z87 has simply been copied over. However in terms of published information the 'fake' 4 pin fan headers issue seems not to be going away icon_eek.gif

Edit: Having just checked the manual for the Asus Z97 Deluxe, this has all of its chassis fan connectors labelled as PWM. The manual also says "...the chassis fan connectors support DC and PWM modes. To set these fans to DC or PWM, go to Advanced Mode->Monitor->Chassis Fan 1/4 Control items in BIOS..". So a full fan control Z97 motherboard is available from Asus but only apparently at the premium price of the Deluxe."

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Motherboards with 4 pin headers DO NOT use PWM. Read the manual, that fourth pin is a feedback signal in pin. The only exception to this is the CPU and OPT header.

This is typical with most motherboards.... This is nothing new. You need to use a splitter off the CPU and OPT if you want to use 4 fans on a radiator or something.

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Posted

@Enderman

@Nuluvius

 

Asus Z87 Deluxe Fake 4-Pin Headers

 

     That is a lengthy read, but it explains exactly how the "PWM Function" on some Asus motherboards is actually voltage controlled.  The motherboard this gentleman is talking about is an Asus Z87-Deluxe  I own an Asus Z87-A, and the only true PWM fan is the CPU_FAN and CPU_OPT, but CPU_OPT isn't directly controllable via Fan Xpert2, so not ideal.  Going into Fan Xpert2, you see that the CPU_FAN is the only fan that is fully controllable from 0-100%.  The Chassis Fan headers are only controllable from 40-100%.  The reason why it cannot be controlled lower than 40%, is because a minimum amount of voltage is required to run the fans.  The CPU_FAN is the only fan listed as PWM in the motherboard manual, the rest are labeled as +5V.

 

     I recently purchased a Phanteks Enthoo Pro, if you are familiar with the case and its one glaring problem, then you already know where this is going, if not:  The Enthoo Pro comes with a pre-installed fan hub.  This fan hub is only controllable through true PWM, otherwise it has to be plugged into SATA and fans will be run at 100%.  There is a lot of confusion, almost 100 pages worth on OC.net regarding this fan hub and how it works.  The majority of motherboards do not have true PWM fans for their chassis headers, as a result, in order to get the fan hub to work, it has to be hooked up to the CPU_FAN header.  This is a an inconvenience, as motherboard manufacturers "market" their product in such a way to make it seem like chassis headers are true PWM, and confusion ensues.

"I genuinely dislike the promulgation of false information, especially to people who are asking for help selecting new parts."

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@Enderman

@Nuluvius

 

Asus Z87 Deluxe Fake 4-Pin Headers

 

     That is a lengthy read, but it explains exactly how the "PWM Function" on some Asus motherboards is actually voltage controlled.  The motherboard this gentleman is talking about is an Asus Z87-Deluxe  I own an Asus Z87-A, and the only true PWM fan is the CPU_FAN and CPU_OPT, but CPU_OPT isn't directly controllable via Fan Xpert2, so not ideal.  Going into Fan Xpert2, you see that the CPU_FAN is the only fan that is fully controllable from 0-100%.  The Chassis Fan headers are only controllable from 40-100%.  The reason why it cannot be controlled lower than 40%, is because a minimum amount of voltage is required to run the fans.  The CPU_FAN is the only fan listed as PWM in the motherboard manual, the rest are labeled as +5V.

 

     I recently purchased a Phanteks Enthoo Pro, if you are familiar with the case and its one glaring problem, then you already know where this is going, if not:  The Enthoo Pro comes with a pre-installed fan hub.  This fan hub is only controllable through true PWM, otherwise it has to be plugged into SATA and fans will be run at 100%.  There is a lot of confusion, almost 100 pages worth on OC.net regarding this fan hub and how it works.  The majority of motherboards do not have true PWM fans for their chassis headers, as a result, in order to get the fan hub to work, it has to be hooked up to the CPU_FAN header.  This is a an inconvenience, as motherboard manufacturers "market" their product in such a way to make it seem like chassis headers are true PWM, and confusion ensues.

Sorry but thread necroing is not allowed on this forum. This topic was started over a month and a half ago. Please read the CoC.

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Sorry but thread necroing is not allowed on this forum. This topic was started over a month and a half ago. Please read the CoC.

You're kidding right?  You replied so fast that you didn't even read that article, or what I wrote, which shows what the difference between True and Fake PWM is.

 

I am doing research trying to solve a problem, that a lot of people have, and I find the answer.  Keep in mind this thread is was one of the top hits, its only a month old and my post can possibly help people. 

"I genuinely dislike the promulgation of false information, especially to people who are asking for help selecting new parts."

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You're kidding right?  You replied so fast that you didn't even read that article, or what I wrote, which shows what the difference between True and Fake PWM is.

 

I am doing research trying to solve a problem, that a lot of people have, and I find the answer.  Keep in mind this thread is was one of the top hits, its only a month old and my post can possibly help people. 

4.3 Thread Necroing

Thread necroing consists of reviving a previously resolved, settled, or "dead" thread after a prolonged period of time by the OP with the intention of bumping the thread to the top of the board. Threads with an activity gap of 1 month or greater that are brought back to the front page is considered "thread necroing". A shorter duration may be considered when dealing with situations like previously resolved threads being reposted or simply for the purpose of bumping it to the front page. Build logs are exempt from this rule.

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"...The fans also do not start up themselves when the PC is turned on, which I believe is caused because Asus' Fan Xpert from Ai Suite II doesn't ramp them up full speed on boot...."

 

Please enlighten me as to how not?

That's normal. The preset quiet fan profile is supposed to turn the fans off at low speed. It's a new feature that came with fanxpert 2.

https://www.youtube.com/watch?v=4i-aTUMuIB0

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