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Thread: EP45-DS3 sys_fan2 problem




  1. #1
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    Default EP45-DS3 sys_fan2 problem

    Hi,

    It seems the 5V and 12V pins are reversed on the 4 pin sys_fan2 header on my motherboard?

    Hence any 3 pin fan i have connected to the 4pin header runs at a lower rpm.

    i.e. 700+ rpm as compared to 1100rpm at full speed.

    The pwr_fan and sys_fan1 (both 3 pin headers) work fine.

    Is there anyway i can fix this? I would like the fan to run full speed as its a 120mm fan.

  2. #2
    Lsdmeasap's Avatar
    Lsdmeasap is offline GIGABYTE Guru
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    Default Re: EP45-DS3 sys_fan2 problem

    What do you have the BIOS fan settings on? If you really believe this is the case, you could easily switch the pins around in your fan connection plug but I doubt this is the case

    Try setting your fan control to Voltage

  3. #3
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    Default Re: EP45-DS3 sys_fan2 problem

    I read that from some other online forums.

    The F9 bios for my Ep45-DS3 doesnt have any speed controls for sys_fan2, only for the CPU fan, even after hitting Ctrl-F1.

    The pins on my fan come as a set of 3 so i cant swap them around...

    I'm using SpeedFan now to set maximum rpm, that means i have to start the program every time i reboot. i was looking for a more permanent and easier way to do so...

  4. #4
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    Default Re: EP45-DS3 sys_fan2 problem

    Here are some links to the other forums where this problem was reported...

    http://forums.tweaktown.com/f69/ga-e...headers-27511/

    EP45-DSR sysfan readings - PC Perspective Forums

    silentpcreview.com | View topic - Gigabyte 4-pin sys fan, 5V vs. 12V?

    Maybe a future bios revision would provide a Bios speed control?

  5. #5
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    Default Re: EP45-DS3 sys_fan2 problem

    Here's the deal as I understand it-

    From Janus Yeh, GB support:
    "CPU_FAN connector needs a CPU cooler with four wires were the PWM modulator is included in the cooler. The mobo senses the CPU temperature and managing the pin 4 signal, the cooler's fan will automatically be increased or decreased, following the CPU temp. Fan's rotation feedback returns via pin 3 for BIOS alarm feature.

    SYS_FAN2
    connector needs any fan, with three or four wires (don't care) since the speed is controlled via on-board PWM controller that supply pulse-width-modulated 12v for the fan via pin 2.
    So, if using a four wire fan, its internal PWM is locked to full speed (this explain that fixed 5v on pin 4).
    This time, the mobo senses the North Bridge (in my case the P35) temperature and will increase or decrease the speed of the fan connected in this socket. Feedback is sent to pin 3 for BIOS alarm purposes.

    SYS_FAN1 and PWR_FAN are three pin socket with fixed full speed fan. No controlled rotation at all from the mobo. Rotation feedback also monitored via pin 3 only for BIOS alarm purpose."

    A normal four pin (not a two or three pin 'tap' into a four pin drive supply molex) PWM fan works thus:

    Ground on pin1
    +12VDC supply on pin 2
    Rotation sensor on pin 3
    5V PWM signal on pin4

    The PWM signal is switched at a set frequency, and 'tells' the fan's on-board 12V power switches when to turn off or on - the average available to the fan being determined by the On/Off duty-cycle ('pulse-width', or, as VorlonUK calls it more accurately "mark to space" ratio) of the pin4 signal. The SYS_FAN2 header makes it possible to use either a three pin standard, or a four pin PWM fan with alacrity. In the case of the three pin fan, pin 2's 12V supply is pulse-width modulated by the board to regulate the speed; in the case of a four pin PWM fan, the 5VDC 'steady-on' signal on pin4 'locks on' the switches on-board the fan, and the modulated power available on pin2 is passed-through directly to the fan...<!-- / message --><!-- sig -->

  6. #6
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    Default Re: EP45-DS3 sys_fan2 problem

    hmm. so the more 'advanced' PWM function is working against the 3pin fans with no PWM capability...

    if so, using a 3 pin fan, is there anyway to 'trick' the m/b into thinking there is a 5VDC 'steady-on' signal on pin4, so that it would provide 12V on pin2?

    or is there a way to make the m/b provide 100% fan duty cycle?

    There doesnt seem to be an option in the F9 bios to control the speed.

  7. #7
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    Default Re: EP45-DS3 sys_fan2 problem

    seems to be confusion as to signal 'directions' here - pins 2 and 4 are 'out' from the motherboard to the fan; pin 3 is the only 'in' from the fan to the MOBO; and pin 1 (ground) is, well, ground...

    Unfortunately, I do not have my system up & running yet (just finished tweaking the MOBO cooling - case & fan controller surgery next...) so I can't tell you if/where in the BIOS to manage SYS_FAN2, or if you maybe need a 'run-time' utility like GB's "EasyTune" or SpeedFan...

  8. #8
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    Default Re: EP45-DS3 sys_fan2 problem

    Yup i'm using speedfan to set the rpm to full now...

    But i would prefer to manage it without launching an additional program on startup.

    Maybe via Bios, command-line or batch files? Is there any way to control fan speed using command-line?

  9. #9
    Lsdmeasap's Avatar
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    Default Re: EP45-DS3 sys_fan2 problem

    Maybe you can use a different fan header if you have one free? That would be what I would think about first, is there another fan in your system that would run ok at that slower fan speed you could switch with?

    You could also buy a 3.5 Bay controller for about $10-15 if you have the spare cash

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