Confused about Nexus/Yate Loon 120mm Fans and PWM

Control: management of fans, temp/rpm monitoring via soft/hardware

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zubblwump
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Confused about Nexus/Yate Loon 120mm Fans and PWM

Post by zubblwump » Sun Jan 07, 2007 11:42 pm

I thought I had this down, but after reading the first post in viewtopic.php?t=16393, Im again confused.

Specifically this quote:
The Nexus "Real Quiet Fans" are astounding fans in the 80mm, 92mm, and 120mm categories. They work flawlessly on PWM...
I thought a 4 pin fan was needed for PWM to work? Is this true?

I'm looking at 120mm fans for a potential future XP-120 install, but am not sure what fan would be best in my situation. I have an ASRock 939 Dual-VSTA motherboard, with a 4 pin PWM fan connector. Would I be better off using one of the JMC 4 pin PWM fans, a Nexus with a Fanmate or similar control, or a Nexus plugged directly into the motherboard? If I go with the latter, does the motherboard still controll the fan speed, or does it run at full speed all the time?

Am I missing some key bit of information here?

pcy
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Post by pcy » Mon Jan 08, 2007 1:34 am

Hi,

Yes - PWM fans require 4 pins - Ground, 12V, Sensor, PWM.

If you plug an ordinary 3 pin fan into a PWM header it works fine, but it runs at full speed the whole time.

Some motheboards have a Bios option to vary the 12V voltage line rather than output a PWM signal.

I have been using Globalwin fans on the XP-120. They have a ceramic bearing which is good for the higher temperatures you sometimes get on CPU fans, and runs more smoothly (quieter) than ball bearing fans.

I'm using them with a PWM->DC converter. They will be an option on my quiet PaQ case (soon to be released) but I'm thinking of selling them separately.





Peter
Last edited by pcy on Mon Jan 08, 2007 3:57 am, edited 1 time in total.

jaganath
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Post by jaganath » Mon Jan 08, 2007 3:00 am

I thought a 4 pin fan was needed for PWM to work?
There are two kinds of PWM, one for 4-pin fans and one for 3-pin fans. The type that works with 3-pin fans sometimes makes fans produce electronic noise, which is why the 4-pin type was introduced. If you have a 4-pin header I would get a 4-pin fan.

Bluefront
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Post by Bluefront » Mon Jan 08, 2007 3:15 am

Add this to the confusion.....3-pin Yate Loon/Nexus fans do not work well with PWM controllers, not all types/brands anyway. I've had really bad results. YMMV

Shaggy
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Post by Shaggy » Mon Jan 08, 2007 5:48 am

3-pin fan & 3-pin pwm header = fan works in pwm mode, it will make more or less noise depending on which fan you use.
3-pin fan & 4-pin pwm header = motherboard supports pwm but the fan doesn`t work in this mode, it works at full speed instead.
4-pin fan & 3-pin header = motherboard doesn`t support pwm and the fan, of course, doesn`t work in pwm mode; it works at full speed instead.
4-pin fan & 3-pin pwm header = i`m not sure, but i think the fan should work as in the first case.
4-pin fan & 4-pin pwm header = fan works in pwm mode, it doesn`t make audible noise (due to pwm), and the speed sensor is suposed to work correctly.

cmthomson
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Post by cmthomson » Mon Jan 08, 2007 2:52 pm

pcy wrote:Some motheboards have a Bios option to vary the 12V voltage line rather than output a PWM signal.
In particular, high-end Gigabyte and Asus motherboards (eg, P5W, P5B, DQ6) have a BIOS option to operate the CPU or chassis 4-pin headers in 4-pin mode (PWM option) or 3-pin mode (DC option).

In PWM mode, pin 2 is constant 12V, and pin 4 is a high-frequency low-power PWM signal used by electronics in the fan to control the fan's speed. The tachometer (pin 3) runs off the constant 12V line.

In DC mode, pin 2 is a low-frequency high-current PWM output that directly modulates the fan's speed, but often has the side-effect of making the fan click. This is because 3-pin PWM is not a steady duty cycle. In order for the tachometer circuit to work reliably, the PWM controller periodically puts out a wide 12V pulse which accelerates the fan and makes it click. With some fans this is barely noticeable, while with others it is noticeably unbearable.

jaganath
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Post by jaganath » Mon Jan 08, 2007 3:06 pm

In DC mode
It's a bit of a misnomer to call it "DC mode", it's still a type of PWM. Not criticising you, but the manufacturers.

zubblwump
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Post by zubblwump » Mon Jan 08, 2007 4:19 pm

OK, so I guess the comment about Nexusfans working flawlessly with PWM must be referring to the 3pin variety then? So then it comes down to a Nexus with a Fanmate or a JMC 4 pin fan. Can anyone tell me which is a better option?

Can the JMC stay silent or near silent throughout its operating range with a 4 pin PWM? Or does it get loud at the top end?

Can the Nexus be set at a constant voltage (through the use of a fanmate) that both keeps it near silent and keeps the CPU cool under full load.

This is being used on a X2 4200+ (89W)

fabre
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Post by fabre » Tue Jan 09, 2007 12:31 am

I also have 939Dual-VSTA and I am running a 92mm JMC fan on it.

At 10% it's dead silent and is sufficient to keep my Cpu at idle in the low 30
On load fan will ramp slowly to maintain the target temp set in the bios.

Once the revs increase fan quickly become audible, which I don't really mind, and I actually find it's kind of reassuring to hear the fan ramp up, especially since at 10% so fan is so slow the motherboard can't even register it's speed.

In 92mm I just discovered an alternative to the JMC, apparently Evercool is also making a 4pin fan, don't know if they are making a 120mm.
http://nexfan03.stores.yahoo.net/92x92x ... m12bp.html

The main annoyance with this, is that on boot the fan run full speed (3200 RPM) for 2min before ramping down.
It's actually the only time you hear it full speed on my XP-90 even under heavy load I don't think it ever went above 50%

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