Motherboard connections

By bob2006ty ยท 11 replies
Aug 24, 2009
  1. Psu cable and case fan cable questions.
    Hi I have a foxconn m61pmv motherboard and a foxconn case, the case fan i plugged into the sys fan socket, but the case fan plug has 3 holes whereas there are 4 pin protruding from the motherboard's sys fan socket, is this a problem?

    ok last question. My psu has both a 24 pin atx power connector to the motherboard (plugged it in) but also a 4 pin atx 12v connector ( i also plugged this in, do i need them both plugged in or just one, (i think the 4 pin powers the cpu and the 24 pin the motherboard, in which case they both need to be plugged in, is this correct? Or do they both power the motherboard, and only one needs to be used, which is it? I read the motherboard manual and it isn't too clear on this.

    Ps i have everything else sorted, I just don't want to turn on the power and fry my hard work.

    Thanks, Bob.
  2. Ritwik7

    Ritwik7 TechSpot Chancellor Posts: 1,672   +9

    Just take a look at the PSU and mobo manual.

    I think you could safely plug in the 3 pin fan connector. (But do Google a little to be sure.) 4 pins usually makes it a PWM Fan.

    And both the 24 and 4 pin connectors should be plugged in. The 4 pin atx must be near the CPU right?
  3. bob2006ty

    bob2006ty TS Rookie Topic Starter Posts: 48

    yes it is near the processor (4 pin), thats that solved. I still don't know about the case fan though, i did a google and came up with nothing.
  4. bob2006ty

    bob2006ty TS Rookie Topic Starter Posts: 48

    the 4th pin on motherboard is the control or pwm pin, so am I right in thinking it doesn't matter if i leave this off. it just means the fan is always on. It would be nice to enable pwm in bios, could i get some kind of adapter?
  5. captaincranky

    captaincranky TechSpot Addict Posts: 13,010   +2,536

    3 and 4 pin fan connectors have the same order of wires. The "extra" pin is the blue wire, and yes, it is the PWM signal wire. Both 3 and 4 pin fan connectors have a safety tab to prevent you from making a mistake.

    If you use a 3 wire fan on a 4 pin all the only difference is, you then have to control the fan speed externally. A 3 pin fan on a 4 pin mobo socket should run natively at full speed.

    Some motherboards have 4 pin connectors for system fans in addition to the CPU PWM fan. the rules above apply to them as well.
  6. bob2006ty

    bob2006ty TS Rookie Topic Starter Posts: 48

    great thats what i wanted, but how would i go about controlling the fan speed "externally" what do you mean by that?
  7. captaincranky

    captaincranky TechSpot Addict Posts: 13,010   +2,536

    Some aftermarket CPU heat sink fan units have speed controllers built onto the unit, or a speed controller that attaches to the case.

    You should take note that the 4 wire socket near the CPU, must ONLY be used for the CPU fan.

    Many of the aftermarket CPUI heat sink fans are coming through with 4 wire PWM fans. Do you have a make and model on the things you're trying to put together?

    In regards to your original question, ATX motherboards have either 20 or 24 pin main power connectors, but, the 4 pin plug that goes to the CPU, is in addition to, and separate from, the 20+ 4 connectors on the PSU.
  8. bob2006ty

    bob2006ty TS Rookie Topic Starter Posts: 48

    foxconn m61pmv motherboard slot marked sys fan (4 pin where the 4th pin is control/modulation/speed control

    and the fan that comes with a Foxconn S-809 Micro ATX Midi Tower PC Case (Black/Silver) with 350W Power Supply

    (3 holes)

    any help to you? ps couldn't find fan name
  9. captaincranky

    captaincranky TechSpot Addict Posts: 13,010   +2,536

    Anytime there's "holes", that's a "female connector". Likewise, anything with "pins", would be the "male" (terminals), which in this case are on the board.
    The fan that is already installed in the case doesn't even have to be connected to the motherboard, it could also be adapted via a "molex" connector, and connected directly to the PSU. (Google "molex" for a picture).

    The board should also have a 4 wire connector marked "CPU fan". The "system fan", is considered to be the fan installed in the back of the case.

    If I haven't resolved your confusion, I'll download the motherboard manual later and check it out.
    BTW, what CPU and heat sink fan are you installing?
  10. bob2006ty

    bob2006ty TS Rookie Topic Starter Posts: 48

    yeah that solved it and its a AMD Athlon 64 X2 Dual Core 5200+ AM2, Retail with Fan

    the processor and fan fit perfectly, no need to worry about the compatibility of the other parts, i have that down, and yes the cpu fan is connected to the cpu fan slot, with the exact same no of pins.

    can you suggest a link to the molex cable i require, couldn't find anything on their site, also if i connect the fan to the psu instead of the mobo will it just run all the time? or will i be able to control it?
  11. captaincranky

    captaincranky TechSpot Addict Posts: 13,010   +2,536

    Much of the time case fans are supplied with what they call, "3 to 4 pin adapters", then you get your hopes up and think they are going to be 4 pin PWM, but no such luck. It almost seems that your case fan should have come with a molex adapter or a molex plug outright. most times they do.

    I really know very little about suppliers in the UK, what with me being over here in the colonies and all that.

    Whether you attach the 3 pin fan wire to your motherboard, or with a molex directly to the PSU, you will net the same result, the fan will run at full speed. This is good or bad, depending on point of view. You will get the maximum cooling obtainable from the fan, but sadly, the most noise also. I guessing that your Matx case has a small fan, which will tend to make more noise than a larger one, due to much higher RPM..

    Arctic Cooling makes a line of PWM controlled case fans. You can look at them here at Newegg; 50002107&name=ARCTIC COOLING

    These are four wire PWM fans and would be controlled by the BIOS in the motherboard.

    The case seems to be a UK or Australian offering, since all the hits I received off the case number where in places like "Perth". The site where you purchased the case just says the case has a fan, no mention of size.
    This case; seems to be a rough equivalent to yours, and it carries a 90mm rear fan.

    A controller panel is another possibility; as is a variable speed fan.

    In any event, the fan has to run fast enough to get the case and CPU cooled down to workable temps.

    Now I have a question, is the "VAT" tax in the UK only, or in Australia also?
  12. bob2006ty

    bob2006ty TS Rookie Topic Starter Posts: 48

    Uk has vat, no vat in australia they have gst which is 10% and already in the price, the vat would only apply in the uk in this case i believe.
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