P4C800E Dlx and Fan Speed Control ???

Discussion in 'Asus' started by Walt, May 20, 2004.

  1. Walt

    Walt Guest

    I can get both BIOS's own Q-FAN, and the SpeedFan Windows
    application to successfully vary the speed of the CPU fan.

    However, I can't get either to vary the speed of either
    the power supply (PWR) or case (CHA) fans.

    Has anyone else worked with fan speed control with this
    motherboard? If so, how successful have you been in
    controlling the three fans (CPU,PWR,CHA) ???

    I am going to be pretty disappointed if ASUS once again
    screwed up their MB wiring and fan speed control isn't
    fully possible. ASUS already got me once with NO fan
    speed control on my old P4B266-C. :(
    Walt, May 20, 2004
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  2. Walt

    Daniel Misch Guest

    You need to disable Q-Fan in Bios, and in SpeedFan you have to go
    under the 20% limit to notice a change in noise/rpm... So on...


    Daniel Misch, May 20, 2004
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  3. Walt

    Paul Guest

    Q-Fan is intended to control the CPU fan, and uses the
    CPU temperature for feedback about the setting to use.

    I just downloaded the W83627THF Winbond datasheet, and
    this chip has three fan speed controllers. They are not
    the normal PWM (pulse width modulation) controls, but are
    a simple 0-5V level instead. This requires a buffer circuit
    to drive the 12V fan, and those cost a few extra pennies.


    I only see a transistor around the CPU fan header. (The op
    amp to drive the transistor could be housed in a quad device
    elsewhere on the motherboard.) The other fan headers don't
    seem to have anything like that. Without a power transistor
    of some sort, it won't be adjustable. (And, the analog
    control method is better for the fan, but kicks off more
    heat from the power transistor itself. PWM solutions
    run cooler.)

    As for the transistor next to the CPU, when the fan speed is
    low, the transistor will have 5V across it, leaving 7V for
    the fan. At a 200ma current level, the transistor dissipates
    5V*0.2A = 1W, and 1W is a reasonable estimate for a safe power
    limit for an SMT device with 1 sq inch of copper for cooling.
    The manual gives some higher numbers for this circuit, and
    the higher numbers might be more appropriate for a PWM fan
    controller (as a PWM'ed pass transistor is saturated or open
    circuit, and is controlled with a square wave signal). I suspect
    the blurb in the manual, about how much current the CPU fan
    can handle, is a copy-paste error. Disabling QFan would cause
    the pass transistor to saturate, reducing the voltage drop
    and the power dissipated, as would setting the fan to a
    higher speed. The worst condition for the pass transistor
    is when the fan speed is low. (Stick your finger on it and see
    how hot it gets :)

    Paul, May 20, 2004
  4. Walt

    Walt Guest

    Yes, I had Q-Fan disabled when I tried SpeedFan.

    I thought the default manual speed controls in SpeedFan always worked?
    Walt, May 21, 2004
  5. Walt

    Walt Guest

    Thanks Paul for taking the time to check this out, and post
    your results!!!

    I guess I just have to accept that once again, have ended up
    with an ASUS board which has limited or no fan speed control.
    Your info, at least, means I don't have to keep searching for
    "better" software. No software will be able to control
    the other fans. :(

    It is interesting that ASUS features (pushes) Q-Fan as a way to
    greatly reduce the fan noise in a PC. However, just controlling
    the CPU fan, and NOT the case fans nor the power supply fans
    will do very little to reduce the overall fan noise. Matter
    of fact, I bet one can't even tell, noise wise, when JUST
    the CPU fan is reduced in speed by 20%.

    Ah, it seems that I have been spoiled by the old P3B-F which
    allows me to control ALL the fans with SpeedFan. :)
    Walt, May 21, 2004
  6. Maybe a bit off topic, Walt, but as you are using SpeedFan, do you know if
    it's possible to control the fanspeed of an Asus Radeon 9600 XT with this
    piece of software? For the reason of asking you this, please take a look at
    my other post about Asus Smartdoctor on Win XP Prof. in this NG today.

    Jan van der Staaij, May 21, 2004
  7. Walt

    Walt Guest

    All I can offer, is to suggest check out SpeedFan's website at

    BTW, I am using Win XP Pro SP1 too, and had no problem installing
    Walt, May 21, 2004
  8. Thanks Walt, I just hoped you could tell me if Speedfan could do the job for
    the Asus 9600 XT before bothering to install it, because I use a Zalman CPU
    cooler and a Thermaltake case and the two of them give me the opportunity to
    control the fans hardwarewise. BTW, my install-problems are not with
    Speedfan, but with Asus Smartdoctor.

    Jan van der Staaij, May 21, 2004
  9. Walt

    Paul Guest

    I would have recommended a drive bay fan controller, but with
    my lousy searching skills, all I've found so far, are the
    manual style (Nexus) controllers. I thought there was at least
    one product out there, that has thermistors for controlling
    case fans.

    The most important thing to provide air flow for in the computer,
    is for the disk drives. They have the tightest environmental
    requirements, and it would be best if inlet air is drawn across
    them without mixing with the other case air. The rest of the
    components can safely take a lot more heat, relatively speaking.

    I just recently bought a P4C800E Deluxe (as I'm not interested
    in LGA775 or PCI Express or processors with large DC leakage
    currents that waste power not related to computing). I checked
    with an ohmmeter, and the two other fan headers have their
    +12V pin connected directly to the +12V pin on the ATX20 pin
    connector. It would seem there is no controlling device in that

    If Q-Fan and Speedfan attempt to control the Winbond chip at
    the same time, I think you can see there would be chaos. Only
    one program should be writing to the fan control register at
    a time, if you want consistent results. Also, from a monitoring
    perspective, only one monitoring program (Asus Probe, Motherboard
    Monitor, Speedfan etc) should be running at a time, as the OS
    provides no semaphore for controlling access to the serial
    SMBUS. That bus runs so slow (10KHz?), it is possible for one
    monitor program to kick off a "read" op on the serial bus, and
    then the OS can schedule the execution of the other monitor
    program, which might just be about to do the same thing. An
    interrupted read op, results in garbage data and a "spike" in
    the smoothed results. (My theory is, it is not entirely possible
    to eliminate this fully, as the BIOS is reading the registers all
    the time too ?)

    Paul, May 21, 2004
  10. Walt

    Walt Guest

    I, too, have only found the manual fan speed controls. I would
    be very interested in one that worked by sensing temps, and
    automatically adjusted the fan speeds appropriately. If someone
    knows of any, please post a reference here!

    Thanks for verifying that Power Supply (PWR) and the Case
    (CHA) fan power connectors are, indeed, connected directly
    to the +12v and thus can't be controlled. Again, I am not real
    happy with ASUS being so cheap. Plus, ASUS advertises that
    this MB, with Q-FAN running, can dramatically reduce system fan
    noise. Without being control the speed of either the Power Supply
    fan nor the any of the Case fans, it simply can't. :(
    Walt, May 23, 2004
  11. Walt

    Walt Guest

    Possibly answering my own question...

    Enermax UC-A5FATR2
    Walt, May 23, 2004
  12. Walt

    Walt Guest

    Thermaltake A1659

    Kingwin TC-02BK
    Walt, May 23, 2004
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