VanguardLH wrote:
> "John McGaw" <nobody@nowh.ere> wrote in message
> news:IcR8j.22862$N67.6793@bignews5.bellsouth.net.. .
>> VanguardLH wrote:
>>> Motherboard: Foxconn N570SM2AA
>>> CPU: AMD Athlon 64 x2 5600+ AM2
>>>
>>> The CPU has a 4-wire fan (black, red, blue, yellow). The "CPU Fan"
>>> header on the mobo only has 3 pins. Using the polarization on the
>>> connectors, the black, red, and blue wires would get connected while
>>> the yellow wire would hang off by itself and not be connected. From
>>> what I can tell, the 3 wires that would get connected are power,
>>> ground, and sense. It would be the PWM (pulse-width modulation) wire
>>> that wouldn't get connected. That means there would be no control on
>>> the speed of the CPU fan. The assumption is that without this
>>> control, the fan would constantly spin at its highest speed but
>>> others have noted that without the PWM line connected means the fan
>>> might spin at high (noisy), medium, or low speed - and low would
>>> probably be too little to properly cool the CPU.
>>>
>>> The mobo's manual shows a 4-pin header for "CPU Fan". That is NOT
>>> what is on the mobo which only has 3 pins. Next to the 3-pin "CPU
>>> Fan" header on the mobo is a 4-pin "J4" connector. It is bare (just
>>> the 4 pins in a row and no plastic polarizing body). The J4
>>> connector is not mentioned in the hardcopy of the manual included
>>> with the mobo nor in the online copy of the manual. So while J4 has
>>> 4 pins with no polarizing plastic body and is next to the 3-pin "CPU
>>> Fan" header, I haven't been able to determine is that is where I plug
>>> in the 4-wire CPU fan.
>>>
>>> For a picture of the mobo, look at:
>>>
>>> http://www.foxconnchannel.com/produc...8EKRS2H-PS.jpg
>>> It shows a 4-pin header for the CPU fan. What I actually got on the
>>> mobo is a 3-pin header marked "CPU Fan". The pictures are lying.
>>> The specification for that mobo says that it supports 7 (seven)
>>> internal SATA ports and which I have. There are only 6 shown in the
>>> picture. If you look closely at the picture, up by the 4-pin Molex
>>> connector on the mobo is a square chip and right by it are solder
>>> pads for the 7th SATA port missing in the picture but is on my mobo.
>>> Also, the specs say there are 3 internal USB headers, not the 2 shown
>>> in the picture (the 3rd is where the solder pads are in the lower
>>> left of the pictured mobo).
>>>
>>> Remember the "J4" labelled 4-pin header that I mentioned might be a
>>> possibility for connecting the 4-wire CPU fan (just a guess, though)?
>>> Nope, it's not in the picture but the solder pads are there in the
>>> picture (to the right of the *pictured* 4-pin CPU Fan header and
>>> underneath the tall black heatsink).
>>>
>>> Apparently when Foxconn decided to upgrade this mobo to add the
>>> missing connections (since the chips were probably already there)
>>> they chose to change from a 4-pin CPU Fan header to just a 3-pin
>>> header. That sucks. Now I have to figure out if I want to return the
>>> mobo to Newegg and find a different one or figure out how to get the
>>> PWM function of the 4-wire CPU fan to work with a 3-pin header (or
>>> find out what the undocumented J4 4-pin header is for).
>>
>> This article is from Intel and is specifically about their
>> motherboards but it should apply equally to others:
>>
>> http://www.intel.com/support/motherb.../cs-012074.htm
>>
>> If your motherboard supports fan-speed control on the 3-pin connector
>> then it should work with your 4-pin fan. The method used will be
>> different and possibly not so precise but it should still work.
>
>
> Thanks for the article link. Be nice if they showed what color was each
> wire. Presumably the polarizing plastic body is how the plug and header
> are to be oriented (i.e., black, red, and blue are connected and yellow
> hangs off unconnected). Hopefully without the PWM wire connected the
> fan will rotate at maximum speed.
>
> I'm using Speedfan on mobos where there are only 3 wires on the fans.
> Since this also uses PWM to control the duty cycle of the fan, I have to
> wonder how it works. Is the PWM applied against the power supplied to
> the fan (i.e., by applying a duty cycle on the power input to the fan)?
> If so, I wonder if these 4-wire fans with a separate PWM wire will
> handle PWM on their power wire.
This is the description of Intel's fan. This may be different than
how the AMD Athlon64 retail one works. (I hate the AMD site enough
now, that I don't dredge for tech info there any more.)
http://www.intel.com/support/process.../CS-022300.htm
"This active thermal solution does not support variable voltage
control or 3-pin PWM control. If this fan is plugged into an older
3-pin connector the fan RPM will default back and then be controlled
by the thermistor located on the fan. When operating in thermistor mode,
the fan speed will vary based on the inlet (T-inlet) temperature
located at the fan."
But I believe Asus motherboards in the past, have supported both
control methods, and they were selectable in the BIOS. (Voltage control
or PWM fourth-pin control.) Later boards seemed to drop the three pin
method, which means they'd only have the fourth-pin control. I don't
know what the history is for other manufacturers.
I think Intel doesn't want the +12V pin voltage varied, because
of the danger that the high side MOSFET won't saturate properly,
leading to a high thermal dissipation situation in the MOSFET.
Page 29 here, shows the old style three pin control method. I think
this is a PWM, but applied via transistor and cap to the 12V supply
pin on the fan.
http://www.winbond.com.tw/NR/rdonlyr...0/W83697HF.pdf
And page 2 here, shows two diagrams for what is inside the fan.
The four pin fan has a MOSFET on the high side, which modulates
the coil current directly. One reason that the PWM operates at
25KHz, is so this method won't be audible on the four pin fan.
http://www.analog.com/library/analog.../fan_speed.pdf
Paul