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Will 4 pin CPU connector take 3-pin fan?

Discussion in 'Hardware' started by Mulderator, Sep 11, 2005.

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  1. Mulderator

    Mulderator Thread Starter

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    I'm going to get this heatsink:

    http://www.newegg.com/Product/Product.asp?item=N82E16835109118

    to cool my Pentium D 830 processor. Problem is it needs its own cooling fan and I'm going to get this one:

    http://www.newegg.com/Product/Showi...eeve+Blue+LED+Light+Case+Cooling+Fan+-+Retail

    But the cooling fans all have 3-pin connectors. My mobo's CPU colling fan connector is 4 pin althouth it looks like it could also take a 3 pin where one pin just wouldn't be used. Will 3 pin connectors work? What's the difference?

    MOBO is ASUS P5WD2 Premium.
     
  2. norton850

    norton850

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    Can't answer your question, just providing some info. Most ASUS boards with a 3 pin cpu fan connector have the following layout: With the front of the board to your right, the pin layout from top to bottom or left to right is rotation, +12V and ground. That could be what the connector from your fan is expecting. Looking at your manual that doesn't seem to be how things are set up so it's hard to tell if the fan will work.

    I know not much help. Maybe a question for ASUS or Thermaltake if you don't get any other responses.
     
  3. Derrick

    Derrick

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    Mulder that looks like a three pin connector to me , which connector are you referring to?
     

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  4. Glaswegian

    Glaswegian Malware Specialist

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    I bought a new Zalman fan and it only has three pins, whereas the stock Intel fan that came wit the board had four. There was a setting in the BIOS, hardware section, that allowed for a 4 or 3 pin fan. I would guess your BIOS will be similar.

    Regards
     
  5. Mulderator

    Mulderator Thread Starter

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    Yes, mine is similar. And now I understand why there are 3 and 4 pins. In my MOBO, the 4 pin is for controlling the speed of the fan in the BIOS. Its set up Pin 1=Ground, Pin 2 is the power, Pin 3 in the "in" (presumably to measure the rotation) and Pin 4 is for Power Management. Would be nice to have that if I could find a could CPU fan with the four pin connectors.
     
  6. Glaswegian

    Glaswegian Malware Specialist

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    Yeah, I had to disable that because I would keep getting a fan warning when booting. The Zalman has an external control that I can use to change the fan speed as required.
     
  7. Mulderator

    Mulderator Thread Starter

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    This is interesting:

    http://www.theinquirer.net/?article=21875

    Maybe I am better off with 3-pin.

     
  8. Glaswegian

    Glaswegian Malware Specialist

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    Interesting indeed. My Zalman is pretty quiet anyway, and it's max speed is less than 3000 rpm because it's so huge, so I found it easier to disable the Q Fan. I would have thought that Thermaltake would be a quiet fan. My case fan makes more noise than the Zalman.
     
  9. Mulderator

    Mulderator Thread Starter

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    Yes--I have a Zalman Heatsink for my 1.8 Pentium 4 (what I am on now) and it does a great job. But the Pentium Ds run very hot and the HeatSink I linked to above seems to do the best job for an air cooler--I actually found it $20 cheaper on Xoxide, which is surprising because NewEgg is usually very competetive in price. I just went ahead and got the Themaltake adjustable fan as well--I think I'll just adjust it with the external control or just let it run full depending on noise. I let the Zalman run full--didn't even install the speed control because I can't hear it anyway--the case fans make more noise.
     
  10. Glaswegian

    Glaswegian Malware Specialist

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    With you on that one. (y)

    My P4 is a Prescott (or PresHot as it's otherwise known) - running hot seems to run in the family. :)
     
  11. blonde288

    blonde288

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    A two wire fan (typically only used for case fans) consists of a (+) and (-)(ground). Its speed can typically be varied from 50% to full, by varying the voltage applied to it from +6 volts to +12 volts. (as it is done using the application of the "zalman mini speed controller" or other...) The motherboard has no idea how fast the fan is running.

    A 3 wire fan has a ground (-)(pin 1), a (+)(pin 2), and a tach wire, sending one pulse for each revolution, back to the motherboard. The motherboard is able to report the exact rpm of the fan this way. On a mobo with fan speed control, the board's fan driver chip would vary the speed of the fan in the same way as the 2 wire method described above, based on it's need or spec. With no speed control, it will send a full +12 volts to the fan (running full speed) at all times, and merely use the tach to see that the fan is turning. (This is how some bios' are able to issue a "fan failure warning", because it didn't receive any tach pulses from the fan, or not enough of 'em)

    A 4 wire fan now adds "pin 4", a pwm (pulse width modulation) wire. The mobo will supply ground (-) at pin 1, a full +12 volts at pin 2 at all times, the fan will return the tach pulse on pin 3, and the mobo will supply a variable width pulse modulation on pin 4, thereby controlling the fans speed accurately and efficiently on this pin. Typically you only see 4 wire fans used on cpu's.

    Using a 3 wire fan on a 4 pin mobo header connector, the fan would run at full speed all the time, unless your bios allows for selectability, as Glaswegian states his did.
    When using a 3 pin fan on a 4 pin header it should be obvious that it's imperative to slide on the connector favoring the correct end of the header.

    For the technogeeks out there, this article should be helpful. ;)
     
  12. Mulderator

    Mulderator Thread Starter

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    Nice summary blondie! ;) Yes, my mobo can change optimize the speed in the bios, but I ordered a fan whereby I can do this with an external controller or not use it at all. My bet is the fan will be quiet enough to just run it full speed like Zalman's fan on its heatsinks.
     
  13. blonde288

    blonde288

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    Thanks, Mulder !

    I am not a big advocate of the use of manual "knob-type" fan speed controls, (typically nothing more than a variable resistor) such as the zalman's. When using the fan at less than 100%, it would require constant monitoring of cpu temps. As an example, just a small drop from 90% rpm to 80% could in a matter of minutes create a core temp rise of 15, 20 or more degrees celcius, depending on the heatsink. Core temp is a correlation of cpu usage, as we all know, that changes constantly. I know I wouldn't want my $280 processor baking away at 88c...

    There are few safe substitutes for mobo control of speed. Best bet is to just buy a quality fan that doesn't make alot of noise, and well designed heatsink.
    I know I'm not revealing any earth shattering new revelation there. :rolleyes:
     
  14. Mulderator

    Mulderator Thread Starter

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    That's true and I did get a good thermaltake fan--about $5 more to get the different options (full speed, heat sensing, and manual control) but I will try it first on full speed and if the sound is reasonable, I will leave it there like I did my Zalman--I did not even install the manual control.
     
  15. Derrick

    Derrick

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    Mulder can you take a pic of the four pin connector for me? , I can't seem to get a clear picture of it anywhere.
    I like that mainboard!! That's the one I would have bought.
     
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