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Playing around with fans

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February 12, 2001 7:32:38 PM

I've been playing around with fans in the last couple of weeks trying to get my CPU temperature down. I've tried adding extra exhaust fans on my PC case. This didn't change anything to the temperature but made the noise of my PC almost unbearable (I have an A7V rev. 1.02 with TB 1200MHz built in an AOpen HX-08 case, and a FOP32-1 cpu cooler). So I took those fans back out. I also tried stacking 2 FOP32 fans on top of each other. This made te temp go down somewhat (about 2 to 3°C, both idle and under load).

Today I tried something else: I have removed the FOP32 fans and have made a costruction using cardboard to fit a 80cm fan on top of the heat sink. The fan is a PAPST 8412NGH which runs at 3600RPM nominal speed and should give 46.5 CFM air flow. These are my findings:

- Runs A LOT quieter than the 2 stacked FOP32 fans
- There's definitely a lot of air blowing out of the heat sink
- Oddly enough, temperature is about 1°C higher than with the stacked FOP32 fans

Anyway, I think I'll leave it like it is now. It runs so much quieter.
Still I wonder why the temperature isn't any lower...

More about : playing fans

February 12, 2001 9:00:58 PM

Air blowing out of the heatsink? Do you mean that you installed the fan so that air blows directly up or is it blowing out from the sides because the air is blowing down onto the heatsink?

T-Bird 800Mhz
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a b à CPUs
February 12, 2001 9:10:26 PM

You need a more efficiant adapter design-the one you made is restricting flow.

Suicide is painless...........
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Anonymous
a b à CPUs
February 12, 2001 9:13:53 PM

Are you doing all this testing with the case cover on?

If so you have probably run into a plateau because the hsf is simply blowing hot air around the case, therefore trying to cool the CPU with already hot air.

First, I would try using one of your fans to blow fresh air into the case, preferably onto the area of your CPU.
The disadvantage about this solution is the noise created by the new fan.

Another possibility is to make your hsf draw air directly from the exterior by cutting a hole into the side of you the case and useing a tube of some sort to guide the outside air into the fan. This should be a little bit louder than it is now, but quiter than a second fan. Temp should go down quite a bit with this solution as well, but at the expense of cutting holes into your case.
February 13, 2001 6:01:46 AM

I actually created some kind of funnel that connects the 80cm fan with the top of the heat sink. The air is actually blown through the heat sink fins, as it is supposed to do. I already have an intake fan which resides at the front bottom of the case.
If I would place an intake fan at the back of the case where the CPU resides, that fan would be located right below the power supply exhaust fan. There's a lot of warm air coming out of there that would (partially) be taken back in that way. (I could of course create some kind of separation between exhaust and intake...)
a b à CPUs
February 13, 2001 6:20:09 AM

Speaking of unbearable noise, my PC has two highflow fans (a 3600 RPM unit in the front and a 4500 RPM mini exhaust fan), a three fan hard drive cooler, and two 7200RPM drives (one SCSI that sound like a turbine). I think I'm going deaf. You can hear my PC everywhere in the house even though it has a very quiet CPU fan! The fans sound more like WHOOSH but the drives really whine!

Suicide is painless...........
Anonymous
a b à CPUs
February 13, 2001 6:57:43 AM

I know exactly what you mean!

I just replaced the low grade fans in my box with three new Sunon high speed fans (standard 80mm, but 2.6 watts and 42 CMF) and they are <b>L O U D</b>

If I had some attachments, I think I could use this baby as a shop vac.
a b à CPUs
February 13, 2001 2:32:12 PM

The funny thing is, my intake fan is quiet, because I had my pick of high-quality fans (I take them out of power supplies) and picked one of supurb design. I had no choice on the rest of the fans (the mini exhaust fan came out of a Mac!) But, the drives and hard drive cooler are the noisiest-I put my hand over the drive cooler and reduced the sound level by about 50%!

Suicide is painless...........
February 13, 2001 2:43:49 PM

How are you measuring those temperatures? I bet you're using the socket thermistor, right? One problem that I've heard of with those is that the airflow from the HSF skews the readings (depending on what direction it's blowing in) - you can end up reading a higher temp in the socket even though the CPU core is cooler. Basically, the more heat you get out fo the core, the more hot air is blowing onto the board.

There's a guy called MikeWarrior who posts on here who's got a very good article on Socket A thermistor readings and why they're no use. Can't remember the URL right now...

Dunc
!