Paul said:
I've got a P4C800-E Deluxe with a Prescott 2.8 overclocked to 3.4. I
have an sp-94 heat sink and need a better fan. My cpu temps are running
46/116 idle 54/129 under full load. I'm looking for the best compromise
noise to cool fan.
Please all give opinions and experience.
Thanks,
Frank
First off, if you had included a room temperature reading, and
a case temperature reading during the idle and full load tests,
it would have been possible to determine, roughly, what thermal
resistance you are getting currently. Case to room temperature
delta should be 7C or less, according to AMD. Some people have
too high a case temperature, in which case beefing up the
CPU HSF doesn't help. The case temp has to be low, for the
CPU HSF to do its job.
Thermal_resistance in C/W = (CPU_temp - Case_temp)/processor_stated_power
Check the review sites for some curves:
http://www.overclockers.com/articles798/
For raw power, Delta fans get the nod. They make some
pretty powerful fans, but you'll need ear protection if
the computer is next to you.
You do need to use a little common sense, though. You can
use a rheostat to vary the voltage to the fan (or even Q-fan
if it is working on your board), but if you select a really
powerful fan, it may not be possible to operate it at a low
enough voltage, to get the RPMs down. Many fans have an
operating range of 7-12V, while a few will still run from
5-12V. It is better to get a fan that is in the right ballpark
in terms of CFMs, so you don't need to adjust the RPMs too much.
(Based on the curves in the above article, I'd probably start
with a fan at about 1/2 the CFM of that Delta. So, maybe a
92mm 34CFM fan and rheostat would allow an adjustment range.
The author of that article does get a useful range from the
Delta, but my thinking is, you could select a fan that is a
bit quieter.)
Go to Digikey.com and try FBA09A12L1BX or FBA09A12H1BX in the
search box. The BX on the end means they have a tachometer
output. They are 92mm by 25mm deep fans. They use a sealed
sleeve bearing, unlike normal sleeve bearings which are open
to the air. The CFMs are 43 and 57 respectively. The letters
L,M,H,U stand for low, medium, high, ultra, representing how
powerful the fan is. This page is how I got the info:
http://dkc3.digikey.com/PDF/T043/1297.pdf
As I see it, one of the problems with the SP-94 design,
is the dimensions of the fin area of the heatsink are not
square. This means that when the fan is mounted on top of the
heatsink, air spills over the side of the heatsink. While this
may gave a beneficial effect on the components right next
to the processor socket, it represents a waste of air flow.
It means you end up using a much higher CFM fan than would
otherwise be needed, and that means more noise.
Ideally, you want a plenum (air box) that runs from the fan
to the heatsink fins, and doesn't allow the air to escape out
the sides. You may be able to construct something from cardboard,
for example, but for the plenum to work well, the fan should
be lifted a short distance from the heatsink. Building a
framework isn't really as much fun as you'd think (I tried
it once, using sheet metal, and my result wasn't nearly
rigid enough).
I don't really see your temps being too out of line, especially
considering the overclock. If you want better numbers, another
option is water cooling, and that is especially useful if you
are having trouble keeping the case temperature under control.
I've read at least one posting, where somebody "remoted" the
radiator of their water cooling system in another room, so the
noise of the pump and fan wasn't next to them.
HTH,
Paul[/QUOTE]
Thx's Paul, I'll check it out!
Frank
