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So now with manual control of both case and PSU fans, I decided on another
approach for the CPU fan. Again, after removing the thermistor I replaced it with a 20K 10-turn variable resistor. This approach seemed to me to have
fewer "moving" parts. You could also use a normal potentiometer and
mount it on the PCI hatch as well. By the way by shorting out the
thermistor I discovered that the SilenX will run up to 3500rpm with good
airflow if you ever needed it. It also runs very slowly with the thermistor
cable open circuit, maybe about 500 rpm. I doubt it would start reliably.
Initially I fitted the supplied steel fan grill on the CPU cooler fan out of sheer ignorance,
but when I read about the noise that obstructions make especially on the intake
side, I tried not using it and it made a large noise reduction. With tidy
cables the grill isn't even necessary, and that's what made me finally realize that
the mesh of holes I'd drilled for the case fans also weren't that great a solution.
For fan speed and temperature measurement, people talk about Motherboard Monitor 5,
but after discovering that a) its stopped development and b) doesn't support
my motherboard, I found Speedfan ( www.almico.com/speedfan.php )
So after I had tamed the fans, the fan noise could be got really really
quiet. I accepted that some parts would run hotter. This was particularly true for the PSU, but I justified it on the grounds that it is designed to
cope with 300W and I was only using maybe 180W. However after seeing the heat
that was constantly pouring out the back of my PSU, (a cheap replacement
I got a year or two back), I ordered a 300W Acbel product that had a
specified noise level below 23dB but also had active power factor correction,
an 80% efficiency, and a lifetime warranty. Not bad for NZ$50. It runs much
cooler, although I haven't yet got the courage up to take the lid off and void
that great warranty. It has some sort of fan controller inside anyhow.
My PC is mainly an office machine, pretty much in idle
mode mostly. On occasion I get it to do something
chewy like video encoding or large file copies. So while I could turn all
the fans right down, this tended to mean the temperatures tended to rocket
to over 50 degrees when under load. It felt important to me to keep that CPU
from overheating, so I devised a compromise. By setting the CPU
fan to 2300 rpm, and the other fans at 1400 rpm, the CPU idles at around 29-33°C, and gets up to about 45 °C after
a 1GB filecopy at 100% CPU utilization. I found that with no intake
grill, rubber isolation mounts for the SilenX fan (very well balanced and has no rumble) on the CPU heatsink, I could run this fan quite fast
and not affect the overall noise level.
Here's the Speedfan graph of my day
to day office type activity
(Those temperatures are in degrees Celsius). As a side topic for the
sake of experimentation I was curious how good the CPU cooler was without
the fan. This is what happened when I shut the fan down:
CPU temperature with the cooler fan turned off.
For the first couple of minutes it did nothing, then started
rising steadily. After 10 minutes I chickened out and restarted the fan. The
upward trend didn't look healthy, with no obvious equilibrium
temperature this side of the melting point of silicon. But I wanted to know,
and now I do.
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