Ant wrote:
On 1/8/2013 2:03 PM PT, Paul typed:

The fan revving on the 7950 is normal. It's designed to run at
a high fan setting, until the driver loads. Then the fan is turned
down by the driver. There's only one problem with that - if you
happen to boot Linux while using the 7950 (like a LiveCD), the fan
could well stay at the top setting for the entire section. The
driver code might be in the NVidia-produced driver, but
not in the default Linux driver.

Yeah, I saw this behavior too with my old GeForce 8800 GT video card and
the closed NVIDIA binary drivers in Debian. I used to exit X to idle
console mode, but that made my video card fan spin loud and fast.


I hated that behavior enough, I control the video card fan
separately. The setting the driver uses, is now irrelevant.
The fan runs off a separate power path. I adjusted the fan
voltage, so I get the same fan speed as before (when the
driver was under control). It means I have the nuisance of a
few extra wires, right next to my video card.

Is it difficult/hard to do?

I needed some connector pins, connector shells, wires, and
some 1N4000 series diodes.

I made a Y cable for the fan, because my motherboard didn't
have enough fan headers. The Y cable, allows one fork of the
Y to run a regular fan, the other fork runs the video card fan.
My local electronics store has male and female fan cable connectors
I can use.

The video card has a 12V fan on it. On some older fans years
ago, I think they've also used 5V on occasion. So you have to be
careful with what kind of fan it is.

The diodes drop some voltage. I suppose I could use resistors,
or I could even use an LM317 variable voltage regulator, and do a
nice job. Diodes are just a tradition in my ghetto PC projects :-)
The diode drops 0.7V. Putting 7 of them in series
gives a drop of 4.9V. 12 - 4.9V gives about 7 volts for the fan.

If the fan speed isn't fast enough, you take one of the diodes
out of the chain. The diodes dissipate a small enough amount of
power, they don't need special effort at cooling them. If you
do this with a monster 1 ampere fan, then expect smoke :-)
No matter what you use, you always check the power dissipated
doesn't overheat something (volts times current).

+12 ---diode--diode--diode--diode--diode--diode--fan---+
|
GND ---------------------------------------------------+

That's the basic idea.

If you look hard enough, you might be able to find a pre-built
commercial solution. For example, some small company in Germany
was building fan controllers years ago, and that thing may have had
three pin fan headers on it. Then, you could run the video card
fan over to a thing like that, and adjust for the speed you want.

I do things like this, mainly because I can... rather than because
I should. I was just so annoyed about the 100% fan speed, and
just thinking about being treated like that by NVidia, I had to
do something about it. The thing is, if NVidia put their minds to
it, they could have completely automated the cooling function
in hardware. There was no excuse for a 1950's style "wait for
the driver to figure it out" type solution. I know that using
software to fill in "hardware gaps" is popular in some circles,
but eventually it gets a bit old.

Paul