Fan Control on A8N-SLI Premium

[Derek]

I've just bought this board and am using 2 Nexus 120mm fans for the cpu
and chassis fan on a amd64 3500 with scythe ninja cooler, and running
v1009 bios. Great combination for a quiet system, but I can't control
the fan speeds.

I've tried Q-fan in the bios and the lowest setting that causes the fans
to run at full speed is 51 C. When just browsing the net I'm at 33 C on
the cpu (currently this system is not in a case), yet both fans are
still spinning but somewhat more slowly than usual. The speed readings
on the cpu fan is 3000 rpm, and the chassis 42187 both in AiBooster and
same readings in Speedfan. Given that these fans are rated at 1000 rpm
and its very clear they are not running anywhere those speeds something
is quite amiss.

In speedfan there is an advanced setting to reverse the output of the
pwm - if a fan physically slows down but the speed indicator goes up -
this is supposed to fix that - however it doesn't.

I've tried Qfan off in the bios and run just with Speedfan - but
speedfan doesn't seem to be able to control the speeds at all and I have
set the temp./fan relations all up correctly.

Two questions:
1) is this problem motherboard specific (have others got q-fan or
speedfan to work well) or is it due to my Nexus fans (not putting out
sufficient speed signal voltage perhaps?) and
2) what software / fan combinations are working for good fan/temperature
control?

Would be a shame to have to scrap the Nexus fans as they are ultra-quiet
even at the stock speed of around 1100 rpm.

Thanks.

 

[Dirk Pajonk]

Playing around here with this features too.

You'll have to switch the FanX Divisor from 8 to 16 or 2 to 8.
The it wouldn't show rpm above 20000 or so.
The it will show lowspeed!

 

[Paul]

Playing around here with this features too.

You'll have to switch the FanX Divisor from 8 to 16 or 2 to 8.
The it wouldn't show rpm above 20000 or so.
The it will show lowspeed!

The typical fan monitor hardware looks like this:

+---------------------------------------+
| 8 bit interval measurement register |
| |
Clock --- divisor --> increment Fan_Monitor |
| |
| Start Stop |
+---- | ------------------------- | ----|
| |
Fan_pulses ---------------+---------------------------+

The selection of the divisor sets the time base for the interval
measurement. If the software you use is assuming the divisor is
2 all the time, the software will get the wrong answer on this
programmable Asus board. To work properly, the software has to
know what the divisor register is set to, in order to scale the
computed result correctly.

Fan speed measurement is determined by measuring the time
interval between pulses, then inverting the result to get
a frequency. When a fan runs too slow for the divisor selected,
the interval register ends up at 255 (filled). It cannot hold
any more counts. The software cannot tell the difference between
a slow fan (that fills the register to 255) or a dead fan (that
fills the register to 255 as well). That is why when a fan is
slow, the software interprets the content of the interval register
as meaning the fan is at 0 RPM.

Now, why the software cannot just set the divisor to match the
speed of the fan, is the real mystery. Architecturally, it could
be that the software designers consider the BIOS "owns" the
divisor register, but since software designers never discuss how
their programs work, that is purely a guess.

In any case, as Dirk is suggesting, if there is an option in the
monitor software program, to set the divisor value the software
uses for the calculaton, then it should be set to match whatever
the BIOS is doing. The software should really be able to read
the stupid divisor value for itself !

Paul

 

[Derek]

The typical fan monitor hardware looks like this:

+---------------------------------------+
| 8 bit interval measurement register |
| |
Clock --- divisor --> increment Fan_Monitor |
| |
| Start Stop |
+---- | ------------------------- | ----|
| |
Fan_pulses ---------------+---------------------------+

The selection of the divisor sets the time base for the interval
measurement. If the software you use is assuming the divisor is
2 all the time, the software will get the wrong answer on this
programmable Asus board. To work properly, the software has to
know what the divisor register is set to, in order to scale the
computed result correctly.

Fan speed measurement is determined by measuring the time
interval between pulses, then inverting the result to get
a frequency. When a fan runs too slow for the divisor selected,
the interval register ends up at 255 (filled). It cannot hold
any more counts. The software cannot tell the difference between
a slow fan (that fills the register to 255) or a dead fan (that
fills the register to 255 as well). That is why when a fan is
slow, the software interprets the content of the interval register
as meaning the fan is at 0 RPM.

Now, why the software cannot just set the divisor to match the
speed of the fan, is the real mystery. Architecturally, it could
be that the software designers consider the BIOS "owns" the
divisor register, but since software designers never discuss how
their programs work, that is purely a guess.

In any case, as Dirk is suggesting, if there is an option in the
monitor software program, to set the divisor value the software
uses for the calculaton, then it should be set to match whatever
the BIOS is doing. The software should really be able to read
the stupid divisor value for itself !

Paul

Dirk, Paul - Thanks that was very helpful. I've got everything under
control now, and to help anyone wondering, here are the settings I've used:

1) Turn off Qfan in the bios
2) Using the program Speedfan v4.27 (has more controls possible than
Qfan): In the Advanced tab set:
a) PWM to Software Control
b) Fan x Divisor to 32 (at the default value of 8 I lost speed
output below 800 rpm, it now shows speeds down to 300 rpm, and then the
fan stops)
c) PWMout at 3M or 12M (not very sensitive to this number)
3) Of course set your device's temperatures to be controlled by
whatever fans you want and trigger temperatures
4) Also, there is a "Remember it" check box - check that so all
settings remain in effect when you come out of a Resume.

This should work with motherboards that have the IT8712F sensor.

And the Nexus 120mm fans are nearly dead silent at stock 12v 1000rpm, at
800 a whisper and well below the quiet whir of a pair of Samsung drives.