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  1. #1
    Apr 2002

    How does speedfan work?

    How does this proggie adjust the fan speed? Does it change the voltage going through the mobo header? I don't use any of the headers for power...just to monitor the RPMs. Their site it down right now so I can't look there...

    Thanks guys!
    Wow this is old...
    Soyo KT400 Ultra (PE)
    XP2100-B (185x12.5)
    SK-7/Smartfan II
    512 Corsair XMS-3200
    Albatron 4200p-Turbo
    WDJB 80g / Maxtor 40g
    Philips 20x CDRW / Pioneer DVD
    Lian li PC-65 / Raidmax 400w
    19" Samsung LCD 191t
    XP Pro

  2. #2
    Jul 2002
    SpeedFan gets your fan RPM's from the mobo's on-board LPC Super I/O chip. Common manufacturers of this part are ITE, National Semiconductor, Analog Devices, and WinBond. Asus boards commonly have a home-grown Asus chip. Mobo makers love them because they can take care of a dozen or more unrelated functions with just one chip. Because they are so cheap, it is more economical for the motherboard manufacturer to use the on of these chips, even if they leave a significant portion of its functionality unused.

    SpeedFan and other programs of its type (Motherboard Monitor 5, Asus PCProbe, etc.) are programmed to access specific types of these LPC Super I/O chips. SpeedFan's capabilities on your specific system are a function of which Super I/O chip your board has (and thus its capabilities), and if and how the board maker has implemented the capabilities of that chip.

    SpeedFan monitors your fan RPM using the hardware monitor function of the SuperI/O chip. Then it controls the speed of the fans using the pulse width modulation fan controller built into the chip, to vary the speed of the system fan(s) based on system temperature. The exact workings though will depend on how your motherboard implemented the chip's functionality.

    Of course, it goes without saying that the fans need to actually be powered off the motherboard in order for SpeedFan to have any chance whatsoever of controlling them.

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