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CPU fan speed report inconsistent

Discussion in 'PC Hardware' started by Haines Brown, Dec 20, 2005.

  1. Haines Brown

    Haines Brown Guest

    I'm running an Asus A8N-SLI motherboard, and just rebooted for the
    first time in several months. I received at the beginning of the boot
    the message: Warning: Your Computer CHIP fan fail or speed too low.

    But when I enter the Phoenix BIOS setup, I see the following:

    CPU Temperature 37ø C
    M/B Temperature 36ø C
    CPU FAN Speed 3125 RPM
    CPU Target Temperature 72ø
    CPU Fan Speed Warning [1200 RPM]

    So, according to the BIOS, everying is nominal. What could explain the
    initial alert?
    Haines Brown, Dec 20, 2005
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  2. Haines Brown

    Chris Hill Guest

    Fan slow to start. Reboot and see if it happens again. If it doesn't
    shut the thing down for several hours and let it get to room
    temperature and try again. If you get the warning replace the fan.
    Chris Hill, Dec 20, 2005
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  3. Haines Brown

    steve Guest

    I've just replaced a fan that was showing a large drop in speed every
    minute or two. You can't trust a bios snapshot. Monitor the speed for
    a few minutes to see if it is changing.
    steve, Dec 20, 2005
  4. Haines Brown

    Haines Brown Guest

    Thanks: that didn't occur to me. A slow start would certainly spell

    I rebooted three times and the problem repeated itself. Looks like
    I'll have to change the fan. Hope I don't have to replace the heat
    sink with it.
    Haines Brown, Dec 20, 2005
  5. Haines Brown

    Haines Brown Guest

    I realize the BIOS monitor is not very reliable, but I have nothing
    else to go on. The RPM does vary a very little in time (1% ?). That
    suggests the fan is working normally, but I don't see how that bears
    on the issue of a slow start up. A slow startup suggests a certain
    stickyness at low RPM, which might not affect the speed at high RPM. I
    assume that if there is such a low RPM stickyness that it might well
    suggest that one day it will fail to start spinning altogether. If the
    CPU gets too hot, I vaguely recall an audible alarm, but I'm not sure
    at this point. It sure would be nice insurance while I'm deciding on
    whether to replace the fan.
    Haines Brown, Dec 20, 2005
  6. Haines Brown

    Arno Wagner Guest

    Maybe some additional info: The RPM monitor has a very coarse
    resolution (likely the 1% variation you see) and does not
    work outside a specific RPM-range. It has a pre-divider that
    needs to be set right for the relevant RPM-Range. It is possible
    thet you fan is just, say, 20% slower on startup, maybe because
    the bnearings need to get warm or whatever and that this falls
    out of the measurable RPM range for the set pre-divider. The same
    effect could happen if it just need a little longer to reach full
    speed (if it is a low-quality fan, e.g. YS-tech, without fan
    controller and heavy rotor complete spin-up can take a while)
    than it takes the monitor-chip to make its first measurement.

    You may be able to test this by monitring the RPM numbers and slowing
    down the fan a little with your finger (applied in the center of the

    Arno Wagner, Dec 20, 2005
  7. Haines Brown

    Marten Kemp Guest

    IMHO there's no reason why you should have to replace the heat sink.
    Depending on how the fan's mounted you may not even have to remove
    the heat sink from the board and processor. While the fan's off use
    a little canned air to blow the stuff off the heat sink, and while
    the cover's off vacuum out the corners of the case as well.

    -- Marten Kemp
    (Fix name and ISP to reply)
    .... The only thing not wasted on the stupid is a bullet,
    and even that might depend on how many bullets you have
    and how many you might need.
    -M.F.S. on alt.support.childfree 5/03
    * TagZilla 0.059 * http://tagzilla.mozdev.org
    Marten Kemp, Dec 21, 2005
  8. Haines Brown

    Marten Kemp Guest

    Replace the fan. From the Asus site, the A8N-SLI is for a pretty
    fancy CPU. A fan's gotta be a lot less expensive than a new CPU.
    I'm not sure that the audible alarm will go off before the CPU's

    In the meantime, try this: peel the sticker over the center of the
    fan back to expose the end of the shaft and use a toothpick to put
    a *small* drop of something like 3-in-1 oil on the fan shaft.
    _Put the sticker back on_ to keep the oil from getting out and
    mucking up things.

    -- Marten Kemp
    (Fix name and ISP to reply)
    .... "The more corrupt the society, the more numerous the laws." -- Seneca
    "And the more capriciously they get enforced." -- Jack C Lipton
    * TagZilla 0.059 * http://tagzilla.mozdev.org
    Marten Kemp, Dec 21, 2005
  9. Haines Brown

    Haines Brown Guest


    Thanks for the suggestion to oil the fan. If that has no effect, I'll
    proceed to replace it.
    Haines Brown, Dec 25, 2005
  10. Haines Brown

    Marten Kemp Guest

    You're welcome. I just found out that some fans
    don't have the lube hole when I attempted this
    on a noisy power supply.

    -- Marten Kemp
    (Fix name and ISP to reply)
    .... A man has to live with himself, and he should
    see to it that he always has good company.
    -Charles Evans Hughes, jurist (1862-1948)
    * TagZilla 0.059 * http://tagzilla.mozdev.org
    Marten Kemp, Dec 26, 2005
  11. Haines Brown


    Oct 14, 2008
    Likes Received:
    I know this is an old thread, but I ran into a similar problem.

    I had the same problem, except it was the cpu. My fix was to change the CPU Target Temperature to a lower setting, like 53C. Try lowering your CPU Fan Speed Warning to 800RPM.

    I put together a machine with a used asus a8ne mobo, and a new amd athlon 64 fx-57 cpu. I had thoroughly cleaned the onboard chipset fan of any dust, as much as I could, using a pipe cleaner, carefully, and blowing away any loose dust.
    When I first turned my new set up on to check if all the fans were running (and that it wouldn't blow up), I noticed the cpu fan hesitated at start up, then started to fully rotate within a few seconds, but what seemed like an eternity to me. I turned the machine off and waited a few minutes before restarting. The fan started fine, and I thought, yep, cheap oem fan. I went into bios and had pretty much kept the previous owner's bios settings and now and then I would get a 'Warning: Your CPU fan fail or speed too low." during boot. This was annoying as it was random. I did a bios upgrade and that went fine. I still received the random warning. After looking at the CPU settings in bios, I could see nothing wrong, and so I figured it was a faulty cpu fan. I bought a high quality Papst German-engineered 80mm fan just recently, and so changed it out. I was disappointed and in wonderment why I was still getting the warning. I finally disabled the cpu and chipset warnings in the bios, as I could see both fans were rotating fine. That relieved me a bit, but I still had to figure out why, because I didn't know if they were spinning at the proper speed to keep things cool.

    In my motherboard hand book (and I wish they would put more information on what all the settings are for as they really leave you clueless) I was trying to determine what the CPU Target Temperature options were for. What do I set it to?

    BIOS: Power>Hardware Monitor> I could see the current running temperature of my CPU was at 43C. I then changed the settings back to "enabled" for both CPU Fan Speed Warning and Chipset Fan Speed Warning. Now I had the option to select a setting under CPU Target Temperature. It was set to 72C. I scrolled through the selections: 51, 54 57 60 63 66 69 72 75 78 81. I did a search on 72c cpu temperature and all mentioned "That's HOT" 166F!" I don't know why it was set to 72c, but it was the previous owner's setting. So, I thought of my current cpu temperature and changed the target setting to something closer to it, 54c. I then let it boot and didn't get the warning. I thought I'd lower it one more setting, 51c, and after cold boots and restarts I no longer get the warning. I tried to find the specs on my particular cpu to find out what its target temperature is, but so far I haven't found that information.

    What I am wondering is why there are such high temperature choices under CPU Target Temperature in the bios? I was shocked to see the choice goes all the way up to 81C! I don't understand what Target Temperature does in the bios, as in, does it effect the speed of the cpu fan- slow it down or speed it up somehow? I could play with the settings and see how it changes the cpu fan speed, as the fan speed readout is shown under Hardware Monitor.

    I have my "cpu fan speed warning" set to 800RPM's. There is also 1200, 1600, but I do not know what to set this to. I left it at what it was set to by previous board owner.

    Thanks for letting me blab away. It was difficult to find any information on how one should go about setting these options to in the BIOS. I'm not a gamer, so never push my board or cpu.

    Any in put is much appreciated. I'm still in the dark , but just glad to no longer get the warning message.

    Last edited: Oct 17, 2008
    Cubby, Oct 14, 2008
  12. Haines Brown


    Oct 14, 2008
    Likes Received:
    Spoke too soon. I should know better than to say, "It's fixed!" when it is a random warning. It got the same CPU fan fail or too low warning again after a cold reboot.

    I can see the cpu fan speed change when I change the settings for 800rpms, 1200rpm, and 1600rpms, so obviously the rotation is changing.

    I have ACPI ATK 0110 virtual device installed on Windows XP from the motherboard disk, that "unknown device" under Manager I was hoping by installing this driver would solve the problem, but it didn't.

    Time to see if there is an issue with this in a BIOS update. I already flashed it last Spring.


    Edited to add: I already have the latest BIOS update. I searched and found others with this board were having the same problem. One person queried ASUStek and their reply was that the fan was "smarter" than the BIOS, and halts a bit in on a cold boot if the CPU temperature is cool. That is what I saw when I first booted up my new system. So, their reply was to go into BIOS and disable Q Fan Controller. I did, and now do not see the glitch warning.
    Last edited: Oct 17, 2008
    Cubby, Oct 15, 2008
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