mCubed HFX case & Athlon X2 3800+, ideas needed

[Pate]

Hello!

I'm trying to build a fast and silent system (aren't we all?) using Athlon X2 3800+ processor and mCubed HFX HTPC case. This system is actually not going to be a HTPC, I have another machine (Pentium M 760 in mCubed HFX case) that works perfectly as such. This machine is to be my main desktop workstation.

The problem, as you might have guessed, is that the CPU with both cores at 100% load runs too hot. After about two hours of such load, the CPU temp diode reads 69 degrees C, which I believe is too near the max case temp of 71 degrees C for this processor.

I purchased a "Heatpipe Extension Set" so that I could connect both sides (all 4 heatsinks) of the case to the processor, but that did not lower the max temp, it only slowed the time it takes to reach that 69 degrees C.

I guess my first question should be: Am I trying to do the impossible? Is it not possible to run this processor under 100% load in such passively cooled case?

Do you have any ideas what I could do to get the processor to run cooler? The following things I plan to test in the future:
1) Add a large heatsink directly on top of the processor, to see if that lowers the temps a few degrees.
2) Use Cool 'n' Quiet to lower the processor from 2 GHz to 1.8 GHz, and thus the wattage from 89 to 66 (or some such).
3) Use the mCubed's "Safety System" to add a slow 92mm exhaust fan directly on top of the processor (with the added heat sink, possibly).

I'm using a Nexus 350 PS instead of a passive one, as I already originally suspected that I need to have some air circulation within the case in any case.

Thanks in advance for any additional ideas you might have! Obviously I'd like to avoid adding any noise sources to the case or slowing down the processor.

Pate

[El Doug]

at load youre putting out 110W or so - i dont think its possible to run that passive

[Ackelind]

If you haven't already done it, undervolt your processor as much as you can. This will reduce your output wattage.

You could also install a 92mm nexus fan, running at 5V. It will probably not be heard over your hard drive, and it could be set to run only when the temp is high enough.

[Pate]

Thanks Ackelind!

An update: I underclocked (multiplier to 9.5x) and undervolted (1.250 V) the processor, and got it to run at 62 degrees C with both cores at full load.

I am pretty happy with that, I left the machine running overnight at full load and the temps stayed at that level. I can live with a 5% performance penalty when that gets me a passively cooled dual core 64bit processor!

I have suspended the hard disks (and added heatpipes transferring the heat from both of the hard disks to the case heat sinks) so thay are nearly inaudible, the only noise left is the whoosh from the Nexus 350 PS. I will probably get the passive SST-ST30NF PS that belongs to this mCubed case. I had originally hoped the ventilation from the Nexus would keep the hard disks cool, but as that did not work and I needed to add heatpipes for them, I don't have a need for case ventilation any more.

Thanks, now I'm a happy camper (err.. silencer!)

Pate