"Sylvain Menard" said:
Hi,
I just bough an A7V600-X motherboard. The thing is that I want to control
the CPU and case fan speed with speedfan. I have just seen that this board
does not support Q-Fan technology. Do speedfan need this to control the fan
speed? Also, I jut found out that the A7N8X-X board support Q-Fan
technology. Does this mean that speedfan would be able to control the CPU
and case fan speed?
Thanks,
Sylvain
The features for motherboards are listed here.
http://usa.asus.com/products/mb/feature.htm
Q-fan consists of control for the CPU fan header.
Q-fan2 is supposed to be able to control more than one fan
header, and by looking at pictures of motherboards, it looks
like Q-fan2 gives control of CPU and chassis fan headers. (CPU
fan speed set by CPU temp, chassis fan speed set by motherboard
temp.)
For Speedfan to do its work, you need a hardware chip to control
the fan speed. Many SuperI/O chips that have a hardware monitor
in them, have two or three channels for fan control. That is
the easy part.
Now, the tricky part, the part that Speedfan cannot detect, is
whether there is a power transistor next to the fan header. If
you look at a picture of a Q-fan motherboard, there is a MOSFET
right next to the CPU fan header, plus a small electrolytic
capacitor. The power transistor typically implements PWM (pulse
width modulation), which is a fan control method that doesn't
let the MOSFET run hot. The power transistor switches on an off,
as instructed by one channel of the Super I/O chip.
If the power transistor is not present, Speedfan can program
whatever it wants into the three channels of the Super I/O chip
and nothing will happen. That could be what you are seeing.
To see examples of the extra circuitry needed outside a SuperI/O
chip:
Pg.5 (upper right corner) - PWM fan controller interface
(acrobat reader might wish to download chinese fonts...)
http://www.iteusa.com/product_info/file/PC/8712IXCGv2.0.pdf
Click "W83627THF", get 627hf.pdf, see page 38 - Linear fan control
http://www.winbond-usa.com/products/winbond_products/view.phtml?name=PCIC
In PWM fan control, there is a signal operating at a constant
high frequency. The pulse width (duty cycle) varies from maybe
60% to 95%. The circuitry on page 5 of the 8712 schematic, level
shifts from 5V to 12V swihg (transistor Q10), and Q9 pumps current.
The 22uF electrolytic cap filters the pulses, making a fan voltage
of between 7 and 12V - the voltage on the cap depends on the long
term average of the variable pulse width signal. The advantage
of the PWM method, is transistor Q9 should not get hot. That is
because the transistor is either saturated when on, or is completely
turned off, thousands of times a second.
In the linear fan control method of the 627, the LM358 op amp and
the NPN power transistor Q1, form a linear power amp. The amplifier
takes a signal that swings from 0-5V, and makes a signal that swings
from 0 to almost 12V. Since the transistor Q1 operates in the linear
zone, the worst case is when the fan runs at 7V - the transistor
has 5 volts across it. Current times voltage is power, and the
transistor will throw off a lot of heat (half a watt for a 100ma
fan). Notice there is no 22uF electrolytic capacitor in this
circuit, and when visually examining a motherboard, that is an easy
way to tell which control method is being used.
If you want to get Speedfan control working, you would either need
to locate the (unpopulated) component locations on the board,
to put the necessary transistors and other stuff, or build up
a small adapter board using the schematics shown above. (Please
note that Asus does not use the reference schematics shown above,
so you cannot use these schematics as a guide to purchasing
components. It would be pretty annoying to reverse engineer how
Asus has built their circuit, so building a small adapter board
would be much simpler. I've tried tracing conductors on Asus boards,
and it can be frustrating and time consuming.)
An alternative, is a product like this one, for about $55 US.
This Zephyrus, from V L System in Korea, allows fan control
versus temperature, and has multiple channels. But the control
software sucks big time.
http://www.short-media.com/review.php?r=273&p=1
http://www.vlsys.co.kr/English/product_zephyrus.php
I am really surprised at how few good automatic fan speed control
solutions are available. Plenty of manual rheobus solutions but
very few automated ones.
HTH,
Paul
