Fanless cooling of slow processors?

guerby · Post by **guerby** » Sun Mar 25, 2007 5:04 am

Hi,

Is it possible to passively cool a slow or slowed processor? I don't need cpu power, so massive underclocking is ok (it's for a cheap home made Linux router). Target is to use only the power supply fan.

What cheap processors (currently available on the market) are more likely to work in this setting, sempron, celeron? What motherboard offer underclock/undervolt?

Thanks in advance for your advice,

Laurent

PS: most "cheap" power supply seem to be 400W or more these days I wonder if it's good for a probably less than 100W system...

jaganath · Post by **jaganath** » Sun Mar 25, 2007 6:14 am

Is it possible to passively cool a slow or slowed processor?

Yes. actually it is more important to reduce voltage to reduce heat.

What cheap processors (currently available on the market) are more likely to work in this setting, sempron, celeron? What motherboard offer underclock/undervolt?

socket 754 semprons are cheapest, but most do not allow to undervolt below 1.1V. This limits power savings. AM2 semprons allow undervolting below 1.1V, good boards for AM2 are asrock NF4G/NF6G-DVI/Biostar T-force. good board for s754 is Biostar Tforce.

guerby · Post by **guerby** » Sun Mar 25, 2007 6:39 am

jaganath, great to hear this is possible!

For AM2 Sempron, will the stock heatsink with fan off be enough if I undervolt? Do you know of a review URL of someone having tried that?

BTW, what about the Intel side?

Post by **MikeC** » Sun Mar 25, 2007 8:27 am

guerby wrote:For AM2 Sempron, will the stock heatsink with fan off be enough if I undervolt? Do you know of a review URL of someone having tried that?

BTW, what about the Intel side?

Not with the stock HS. You need a HS with much wider spacing between fins. See SPCR reviews of Scythe Ninja and Scythe NCU-2000 to get an idea of what I mean.

Also, if you already have one fan spinning in the PSU, a second fan can easily be added without adding any audible increase in noise. The trick is to choose the right fan, a big open fin HS, and set it to a low enough speed.

A single very slow spinning fan provides so much better cooling than no fan at all. This is guaranteed.

jaganath · Post by **jaganath** » Sun Mar 25, 2007 8:40 am

what about the Intel side?

pentium/celeron M are good when undervolted,but motherboards are expensive. mobile core (2) duo expensive and overkill for your application. standard c2d has high idle power consumption.

guerby · Post by **guerby** » Sun Mar 25, 2007 9:38 am

jaganath wrote:
what about the Intel side?
pentium/celeron M are good when undervolted,but motherboards are expensive. mobile core (2) duo expensive and overkill for your application. standard c2d has high idle power consumption.

Ok I'll stick with AMD for this project (my desktop has a E6600

).

I still haven't been able to find underclock/volters experience on the net with current hardware. Most articles I find date back to 2004. May be the trend is really overclocking now...

jaganath · Post by **jaganath** » Sun Mar 25, 2007 9:52 am

I still haven't been able to find underclock/volters experience on the net with current hardware.

viewtopic.php?p=317052&highlight=sempron#317052

Palindroman@I undervolted my Sempron 3200+ through RM Clock to 0.8 Ghz at 0.8v and 1.8 Ghz (stock) at 1.0 v.

Yesterday I let the system run fanless (except for the PSU fan which is in a separate compartment). Ie I left the boxed cooler on the CPU but didn't plug it in. The CPU remained at a temp of 35 C at idle, and it took half an hour of stress testing to get it to 65 C. I'm building this system for clients so I'll probably leave the CPU fan running at 1100 rpm, just to be sure. But if it were my own computer I'd definitely run the CPU fanless.

Considering you will use PSU fan to provide cooling to CPU, should be no problem.

guerby · Post by **guerby** » Sun Mar 25, 2007 10:08 am

Thanks again! Last piece of information is what was the heatsink for the AM2 Sempron, I'm looking thorugh Mariner and Palindroman post history...

Mariner summary is there:
viewtopic.php?p=315515#315515

bog standard Sempron 3200 ... ASRock ALiveNF4G-DVI ... 1.4GHz at 0.9v ... burn temp 50 degree with standard heatsink

Another report here: viewtopic.php?p=327902#327902

sareiodata · Post by **sareiodata** » Sun Mar 25, 2007 10:44 am

Search Ebay for an old AMD K6-2 or Pentium III @500 Mhz with 64 ram or so. I have an AMD K6-2 @450MHz as a rooter useing Windows XP and I have no problem what so ever...most of the job is done by the two LAN Cards. I have it running for 2 months and only restarted him twice(Windows XP I presume...

).

guerby · Post by **guerby** » Sun Mar 25, 2007 11:43 am

sareiodata, for this project I'm limiting myself to new hardware (don't ask why

).

But indeed I can get in Paris fully working complete old/used PC for about 20 euros (and travel time), and this is indeed an alternative solution.

kater · Post by **kater** » Sun Mar 25, 2007 12:58 pm

Nothing better than a Ninja to passively cool a CPU. Look at my sig. The CPU is pretty beefy (and OC'ed!) and it stays at 34 in idle with rear 120 mm fan and PSU 120 mm fan at their lowest possible RPM - both are impossible to hear from 20 cm. The case has one front 92 mm fan running at its lowest speed - effectively silent at 20 cm. The CPU reaches ca 55 under load (Orthos) with both exhaust fans running at appr. 8-9V. I can crank'em up to 11V but no need for that. Well, it's a fresh setup and I'm so happy with it that I take every opportunity to share this story. Good thng it fits your topic too

Now, I only need to to sth. about that terrible HDD of mine...

guerby · Post by **guerby** » Sun Mar 25, 2007 1:06 pm

kater, the ninja looks impressive but is also not cheap