Difference between 2742rpm and 3400rpm

Posted by John-Erik | Filed under Uncategorized

The difference between 2742 RPM and 3400 RPM is negligable at best as far as airflow in concerned. Are you using heat transfer compound? A termal pad? Phase change material (PCM)? If not, it could easily be the lack of that thermal transfer capability that is preventing it from moving heat off of the CPU, or even the improper application of it would do it.

As a test, if you touch the heatsink, is it imcomfortably warm? If so, then it’s working fine and you need additional chasis airflow. If not, it’s not working fine and you need to reapply the thermal transfer compound. For reference, I have two CPUs one running at 39 and the other at 37 C (I had to do this conversion in my head, so be thankful :P) with 3500 RPM fans running at 3515 and 3629 RPM, respectively. The difference in heat is that Windows favors the first CPU for ALU-intensive work and the heat sensor is right next to the ALU.

You don’t need a new power supply fan, but you may need an additional case fan (a fan that’s mounted in the back of your case and sucks the hot air off of the CPUs and RAM). You shouldn’t need more than one case fan unless you’re running a server, and only then for redundancy. For reference, my system has the power supply fan, the main case fan, two front fans (to force air over the HDDs and expansion cards, not strictly necessary but helpful given how crammed my system is) and a video card cooling fan (takes up an expansion slot).

The only way to tell if it’s a false reading is to plug the fan into another system and see how fast it spins there, and also listen for noise and check the input voltage with a multimeter. If the voltage is fine and it’s not making any noise, it’s spinning at rated speed and you’ll just need to compensate. In MBM5, you can play with the fan type and divider to get it right.

They both have heatsinks and the FireGL has a HSF on it, and I’ve replaced the PCM on the FGL with some better rated PCM (better rated than AS, might I add) and the adhesive on the Rage 128 heatsink with Arctic Alumina, so locally it works fine.

I could add another ventilation fan to the case (it turns out this is what I ended up doing, dumping the USB 2.0 card and moving the Rage 128GL there and adding a squirrel cage fan directly below the FGL, and this works fairly well.

The problem with mounting additional exhaust fans is “where would I put them?”. The two fans in the front are clearly intake, one being used to cool the hard drives and the other ensuring that the rest of the intake is blown over the expansion cards (where it’s needed) as opposed to the removable and optical drives up top (where it’s very clearly not needed), and the air is then drawn rearward and upwards by the primary cooling fan, cooling 1 GB of RAM and two 1.4 GHz Pentium III-S with 512k of cache and the power supply. Even with all of the, my chasis temp is still 75 F (ambient is 72) and my CPU temps are 100 or so at full load, and the heatsinks are barely warm to the touch. I ended up with a squirrel cage blower, which was effective, but I could either vent out of the side of the case through a blowhole (which would have the effect of pulling the airflow such that it doesn’t cool my CPUs as effecitvely) or on top where there would be no airflow thanks to the 500VA/300W UPS right there.

Oh, as for the USB, since I didn’t need 2.0 (I just got the card because it was less than a 1.1 card with fewer ports) I picked up an adapter that moves the front panel USB connectors (since I don’t have front USB ports) to a slot and put it in above the video card in that extra slot.

Permalink | May 29th, 2003

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