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Need Advice on Possible Passive Cooling

Posted: Fri May 19, 2006 4:43 pm
by fastturtle
I'm looking at a Mobo/Geode Combo deal and a massive HS I bought for OC purpose. Don't know the make anylonger but it takes 80mm fan and is rated to cool Athlons OC'd to 150watts

I'm thinking that due to the 14watt TLD of the included Geode NX1750, combined with the HS I've already got, that it would be possible to actually go passive on the cooling. When I got investigating the actual HSF requirements of older CPU's (233 pentiums) turned out the TLD was 20 watts.

Overall, I believe this would be a good candidate for a Passive Cooling Solution, although I don't know if the board will boot w/o a cpu fan. If not, then I have an old Pentium fan (100 rpm/8-10 cfm) that should solve that problem while being silent.

The Combo I'm looking at can be found: http://www.directron.com/m7vig4comb29.html

Anyone who's done a passive cooling project let me know what you think.

Posted: Fri May 19, 2006 5:47 pm
by justblair
I'm passively cooling an undervolted palamino 2100xp. CPU power tells me its running at 32w currently (I think thats under load)

Its running fine. The case has a lot of panels cut out and replaced by mesh. To do so I am using a TT typhoon which isn't even the best heatsink for passive op. The whole PC is passive including the PSU. I have no fans running and the processor stays below 60c

I did mod the typhoon to improve its performance so I dont know how relevent my figures are. It was running at about 22w with no mods done.

I have also modded the mobo with passive heatsinks all round including the power regulation circuits though I suspect that was overkill on my part. The Northbridge has a big copper CPU heatsink, it was a 6cm HS and I haven't trimmed too much of it to make it fit.

So in answer to your question. Yes I would be very suprised if you cant get that combo to run passive.

Posted: Fri May 19, 2006 6:41 pm
by fastturtle
Thanks justblair:

That's pretty much what I thought, especially since I've got a massive HS that's designed to handled an OC'd Tbird.

As to additional heatsinks, I doubt I'll need anything more then the stock ones as the Geode runs so cool. The interesting thing is the specs look identical to an XP1700 except for the TLD rating and since I'm running an XP1800, I doubt I'll see any noticeable loss in performance running it stock.

Posted: Sat May 20, 2006 1:50 am
by jaganath
I doubt I'll need anything more then the stock ones as the Geode runs so cool.
One problem with these Geode combo deals is that the supplied motherboard often doesn't supply the correct voltage to the CPU (stock Vcore for the NX1750 is 1.25V) like 1.4V or higher. The max dissipation of the Geode at stock Vcore is 25W, maybe add 10W for the overvolting, 35W. Borderline passive.

Posted: Sat May 20, 2006 7:33 am
by fastturtle
Hadn't thought of that but since the HS I'm planning on is similar to a Nexus 6400 except all aluminum and a better mounting bracket (3 lugs). The main difference is the fact that it's a single piece cooler that's milled. So there's complete thermal connectivity plus it's appears to be a little larger then the Nexus.

As an early experiment, I'd actually managed to run a 950 Tbird w/o any fan for several minutes without seeing any temp rise although that was only at idle. Based on my experiences with it, I suspect it'll provide adequate cooling without any fan and if needed, I can always go with one of the recomended quiet models and undervolt. The other possibility is to us an cooler for a Pentium 233 as it should provide enough extra cooling to handle the load while still being almost silent. Heck it's even possible to get a new fan for the purpose w/o using one of the chipset coolers. :)

Edit
Just found the HS listed at Newegg and can now state it's the Spire.