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Additional Case Fans Questions

Last response: in Components
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September 17, 2011 6:16:30 AM

Alrighty So I have an ASUS P8P67 PRO that has 4 fan headers:
1 x 4-pin CPU Fan
1 x 4-pin CHA Fan
1 x 3-pin CHA Fan
1 x 3-pin POW Fan.

Currently in my CM 690II, I have one front intake 140mm, one top outtake 140mm, and one rear 120mm outtake. All of these fans are 3-pin connectors. As well as a Hyper 212+ 4-pin fan.

My question:
I want to add 3 more fans to this setup.

An identical pull fan to the Hyper 212+
http://www.newegg.com/Product/Product.aspx?Item=N82E16835103069&Tpk=R4-BMBS-20PK-R0

And 2 more 140mm case fans, another on top and one on bottom.
http://www.newegg.com/Product/Product.aspx?Item=N82E16835103078&Tpk=R4-S4S-10AK-GP

I do not want to add a fan controller, I just want to let the motherboard handle the speed of the fans.

The 4-pin CPU header has a max of 1A, each fan on the Hyper 212+ is only 0.36A. So technically I could get away with something like this, a 4-pin splitter.

Or would it be better to go with something like this , directing the power to the PSU, and would the motherboard still be able to control the fans?

The second part of the question is what should I do with the other 5 fans? Can I split the power with a 3-pin adapter for the top two fans, and one for the bottom/front fans? or should I use something like this then a 3-pin connector to reduce the power output of the motherboard? Would the motherboard still be able to control these fans if I did that?

P.S. I know I am a noob. I have looked at fan controllers like the Sentry 2. Mainly I want something that I can set and monitor without making changes. I like the auto function of the Sentry 2, but still don't want to really mess with the temp probes and such. Which is the main reason that I want the motherboard to control the speeds. Let me know what you think. And thank you.
a b ) Power supply
a b V Motherboard
September 17, 2011 6:39:52 AM

I'm not certain that the BIOS can control two fans on a splitter because you have two fan RPM signals which may cause issues if the fans aren't running at the identical speeds - which they never are. A fan controller would be your best bet... but I have to ask why you want all of these fans?

Too many fans just causes turbulence and noise and does not improve component cooling. In fact turbulence can reduce component cooling if there isn't a nice smooth flow of cool air in and hot air out. More is not always better. You might want to do some testing before getting all caught up in adding more fans.
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September 17, 2011 8:36:21 PM

I have heard if i cut the PWM from one fan they will both be controlled by the motherboard. That is for the CPU.

I guess I don't really need the extra case fans, just worried that the case gets to hot. I overclock my processor to 4.5Ghz, and the processor gets to ~70 C i know the limit is 72 C. I at least think I want to complete the Hyper 212+ with one more fan, but the others are not required. What do you think?

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Best solution

a b ) Power supply
a b V Motherboard
September 18, 2011 2:29:10 PM

The StarTech adapter from Amazon in your link will do the job nicely. It is designed to power two 4-pin fans from one 4-pin header. Look closely and you can see that the middle connector does not have a yellow wire to it. This is proper design - it does NOT send a speed pulse signal from the second fan into the mobo, so the mobo only gets ONE fan's speed pulses and is happy. (The second fan's speed simply is never monitored, so it's up to you to check it periodically to make sure it is still working.) You are on the right track in your calcs of current draw versus available power, BUT the limit is in start-up current, not running current. On that basis, you probably should not try to power more than two fans from one mobo pinout. So this adapter is just fine.

Incidentally, 3-pin fans can plug into 4-pin outputs. So technically you could use this same adapter to connect two 3-pin fans to one 3-pin mobo pinout. When you do this, the connector is arranged so that the PWM signal required for 4-pin fans is ignored, but all three other lines (those required for 3-pin fans) are handled properly.

The Rosewill splitter from Newegg works well within certain limits, and does route the fan power from the PSU directly (via a 4-pin Molex connector) rather than from the mobo. But it still accomplishes fan speed control. Here are the limits:
1. This is only for 4-pin fans, because it uses a shared PWM signal for all three connected fans for speed control. So they have to be PWM (4-pin) fans. Any 3-pin fan connected to this will always run at full speed.
2. Control of all three fans is based on the CPU's internal temperature sensor. Without this adapter, the CPU cooler speed is based on this sensor, and case fan speeds (those connected to mobo SYS_FAN outputs) are based on a different sensor built into the mobo. This adapter just will run the case fans attached to it according to CPU needs. Not really a problem - just so you know the subtle difference.

Two points about mobo fan pinouts:
1. ALWAYS connect the CPU cooler to the CPU_FAN output. This fan's speed will be controlled by the actual temp inside the CPU. More importantly, some mobo's monitor the speed of this fan carefully to prevent CPU overheating and damage. If there is no fan connected to this port (or the wrong fan), the monitoring system is all fouled up with wrong information. That Rosewill adapter does this provided you connect it to the mobo CPU_FAN output and then plug the actual CPU fan into the correct adapter 4-pin socket.
2. The PWR_FAN connector on the mobo originally is intended only to plug into it a special set of leads coming from the PSU. It purpose solely is to allow the fan inside the PSU to send its speed signal to the mobo to be monitored. The port does NOT control the PSU fan's speed - that MAY be controlled internally within the PSU itself. If you have no such connector coming out of the PSU, you normally connect nothing to this mobo pinout. HOWEVER, many mobos actually do provide on this port the Ground and +12VDC signals of a standard 3-pin fan port, but with NO speed control. So if you do not use it for the connection from the PSU, you can plug in a 3-pin fan here - it just will always run full speed.
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September 19, 2011 5:41:24 PM

This is wonderful information. Exactly what I was looking for. Thank you sooo very much!!!
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September 19, 2011 5:41:32 PM

Best answer selected by PsychoStar.
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