Re: P5P800 Variable Intel CPU fan speed
- From: "Ken" <krlorenz@xxxxxxxxxxx>
- Date: Tue, 10 Jan 2006 05:52:41 -0600
Thanks for the information. I think you have hit on exactly what is going
on. When the CPU temp goes to 60+ the MB temp hardly moves from "normal
system idle" 31 degrees. The computer is now sitting in the basement where
it is much cooler than in the den when it would try to "take off". I moved
it to the basement because during the summer it actually made the den a few
degrees hotter! Anyway, I have tried setting the Q-Fan to disable (also
reloaded default BIOS settings per ASUS Tech Support) and the fan runs at
2650 rpm. When I disable the Q-Fan the Q-Fan Mode goes away so I cannot try
Q-Fan disabled and Q-Fan Mode DC. The only part that is a little confusing
is ASUS Tech Support kept telling me the fan should run at maximiun when the
Q-Fan is disabled. Looks to me like the maximum fan speed is closer to 3500
rpm. I guess if I want to try to control the CPU temperature to a lower
level when running DVDShrink in the basement I need to install the Zalman
CU7700 fan sitting on the desk next to the computer... Or... install a small
heater inside the case?!! I sure am lucky I got a good old reliable P4PE
system with the Northwood 2.53 CPU for a second system.
"Paul" <nospam@xxxxxxxxxx> wrote in message
news:nospam-0901061713010001@xxxxxxxxxxxxxxxx
> In article <16OdnfKO2OfG0F_eRVn-sg@xxxxxxxxxxx>, "Ken"
> <krlorenz@xxxxxxxxxxx> wrote:
>
>> I am on my second replacement P5P800 MB from ASUS. The SATA controller
>> did
>> not work on the first one replacement and now on the second replacement I
>> cannot make the Intel cpu fan speed up even thought the cpu temperature
>> goes
>> to 62 degrees C when I am running a cpu intense program like DVDShrink.
>> I
>> have tried the BIOS setting: CPU Q-Fan Control - Disabled and I have
>> also
>> tried the BIOS settings: CPU Q-Fan Control - Enabled, CPU Q-Fan Mode -
>> PWM,
>> CPU Fan Ratio - Auto. Nothing much seems to change, the fan never speeds
>> up
>> even though the cpu temperature reported by ASUS Probe climbs to 62
>> degrees
>> C. I know the fan on the original MB would try to "take off" when I ran
>> DVDShrink. What am I missing or do I have yet another defective
>> refurbished
>> MB?
>
> Pg.59 here, mentions that the PWM control and the thermistor in
> the Intel fan, both work to control the speed. The thermistor
> ramps fan speed between 30C and 38C case air ambient. The PWM
> control is used by features like Q-fan, to ramp the fan speed
> when the CPU die temperature hits 50C. The voltage to the fan
> is gated by both processes (so a low case temp and a high CPU
> temp, means a low fan speed). At least, as far as I can tell
> from this description on PDF page 59:
>
> http://download.intel.com/design/Pentium4/guides/30255304.pdf
>
> What you would have been hearing previously, is Qfan cranking
> up the PWM percentage, when the processor die temp went over
> 50C. If your computer case now is a lot cooler than previously,
> then the ramp will not be a big change. If the case air is at
> 38C or higher, the fan control range via PWM should allow
> the fan's maximum speed to be achieved.
>
> PDF page 133 here, shows various circuits for the fan. Asus
> has probably incorporated both the top left circuit and the
> middle left (four pin) circuit. When the user selects "PWM",
> the PWM lead receives a ~25KHz signal (signal is constant
> frequency, but variable duty cycle square wave), and the
> 12V pin is given full 12V feed. When the user selects "DC", the
> PWM lead is not used (probably floats high), and the voltage
> level on the 12V supply to the fan header is adjusted by
> the two transistor switching circuit. Asus does this, so they
> can support both three pin fans and four pin (retail) fans.
>
> http://www.winbond-usa.com/products/winbond_products/pdfs/PCIC/W83627EHF_EHG.pdf
>
> How do you debug this crap ? Good question :-(
>
> I would take a voltmeter, and probe the +12V wire on the
> Intel retail fan. This should be pretty close to 12V when
> in PWM mode. In DC mode, with Q-fan disabled, maybe you'd
> see 11V or more. In DC mode, with Q-fan enabled, it might
> drop as low as 7V.
>
> If you had an old analog meter, connecting it to the PWM
> signal might show +12V if PWM was disabled and high 100%
> of the time. A lower voltage might show when PWM is enabled
> and a less than 100% duty cycle square wave is being used.
> I would expect a digital voltmeter to give a garbage reading
> if PWM was running, and read a stable +12V if PWM was
> not running.
>
> Have you tried the "DC" setting with Q-fan disabled ? With
> PWM floating high, I would hope the Intel fan would run
> as fast as the thermistor would allow. At 38C case air
> ambient or greater, that should be at the fan's maximum
> speed.
>
> Paul
.
- References:
- P5P800 Variable Intel CPU fan speed
- From: Ken
- Re: P5P800 Variable Intel CPU fan speed
- From: Paul
- P5P800 Variable Intel CPU fan speed
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