What is the most powerful CPU you can cool passively??

Cooling Processors quietly

Moderators: NeilBlanchard, Ralf Hutter, sthayashi, Lawrence Lee

Post Reply
swoody
Posts: 48
Joined: Mon Mar 16, 2009 12:43 am
Location: Chicago, USA

What is the most powerful CPU you can cool passively??

Post by swoody » Tue Aug 25, 2009 1:02 pm

So, I'm looking into specifics for a build that will (hopefully) be coming up soon. I'm looking to make this new build as quiet as possible - aiming for a single 120mm fan. At the same time, I want this computer to be VERY quick. Therefore, I'm trying to find out what the most powerful CPU you can run with passive cooling would be. I would need something that could run 24/7 at 100% and not worry about overheating/damaging other parts. Also, what kind of cooler would you guys recommend for such a setup? Keep in mind that the single 120mm fan will be on the case just behind the CPU heat-sink, so it wold receive some assisted air movement. What are your ideas, thoughts, suggestions? Thanks in advance!

Woody

swivelguy2
Posts: 404
Joined: Sun Jul 04, 2004 9:18 pm
Location: Illinois, USA

Post by swivelguy2 » Tue Aug 25, 2009 1:16 pm

With a little duct, you can turn that "passive" CPU cooler into something that's cooled just about as well as an "active" one. The HR-01 plus is a perfect candidate for that setup. Depending how much air that fan moves, you can probably get away with something like a Q9550.

Another concern, for a system that runs at 100% load 24/7 would be the PSU. If the only fan in the system is occupied with exhausting CPU heat via a duct, what's keeping the PSU cool?

Here's an example: viewtopic.php?t=54394. It's an i7 920 ducted to both the rear exhaust fan and the PSU exhaust fan working together.
Last edited by swivelguy2 on Tue Aug 25, 2009 1:23 pm, edited 1 time in total.

Vibrator
Posts: 94
Joined: Sun May 31, 2009 9:46 am
Location: British Columbia

Post by Vibrator » Tue Aug 25, 2009 1:20 pm

I'm sure a Scythe Orochi can cool something like a Q9550s passively
It's huge though

swoody
Posts: 48
Joined: Mon Mar 16, 2009 12:43 am
Location: Chicago, USA

Post by swoody » Tue Aug 25, 2009 1:45 pm

Well, I'm still not sure about the PSU yet. I'd *ideally* like to run a fan-less PSU, and as far as I've seen they can dissipate enough heat on their own. Am I correct in that, or am I mistaken?

If I had to, I could possibly use the Nexus 430 PSU, which is *very* quiet. It has a 120mm fan on that. Do you guys think that would be enough ventilation for a Q9550 system? If not, I'd probably run either a Nexus or Noctua fan on the rear of the case.

swoody
Posts: 48
Joined: Mon Mar 16, 2009 12:43 am
Location: Chicago, USA

Post by swoody » Tue Aug 25, 2009 2:02 pm

So a ~95w CPU be the highest I could run passively @ 100%, with one fan near it?

Klusu
Posts: 196
Joined: Thu Jul 24, 2008 10:57 am
Location: Riga

Post by Klusu » Tue Aug 25, 2009 2:55 pm

swoody wrote:...one fan near it?
Does the cook put the ingredients into the soup, or near it?
The airflow must go through the heatsinks, not around them.
A fanless PSU makes sense only if the computer is fanless.
One fan can cool the CPU and the PSU.
But two slower fans may make less noise.

Riffer
Posts: 517
Joined: Mon Jan 06, 2003 4:14 pm
Location: Toronto, Canada

Post by Riffer » Tue Aug 25, 2009 3:26 pm

i920 with an HR-01 might be doable if a 120mm rear or PSU fan is pulling out the back of the case. I don't know if I would duct it though, as there are other components could use some airflow, but it might be worth the experiment.

swoody
Posts: 48
Joined: Mon Mar 16, 2009 12:43 am
Location: Chicago, USA

Post by swoody » Tue Aug 25, 2009 4:09 pm

Klusu wrote:
swoody wrote:...one fan near it?
Does the cook put the ingredients into the soup, or near it?
The airflow must go through the heatsinks, not around them.
A fanless PSU makes sense only if the computer is fanless.
One fan can cool the CPU and the PSU.
But two slower fans may make less noise.
Well what I'm saying is that the CPU heat-sink won't have a fan on it, but there would be a case fan mounted on the case, only a couple inches behind the heat-sink. So there will be better air movement.

burebista
Posts: 402
Joined: Fri Sep 02, 2005 12:05 am
Location: Romania

Re: What is the most powerful CPU you can cool passively??

Post by burebista » Tue Aug 25, 2009 9:15 pm

swoody wrote:Therefore, I'm trying to find out what the most powerful CPU you can run with passive cooling would be.
i7 940?

TheAtomicKid
Posts: 95
Joined: Sat Aug 20, 2005 3:01 am

Post by TheAtomicKid » Tue Aug 25, 2009 9:56 pm

I cool a Q6600 passively in my main rig.

Antec Three Hundred enclosure,

HR-01 plus heatsink, mounted crossways so that the long sides of the cooler parallel the ground.

Reverse the top fan on the three hundred.

Enjoy. Also, the spillover from the top fan does a nice job in and around the cpu area/mosfets/etc.

Atomic

PartEleven
Friend of SPCR
Posts: 279
Joined: Sun May 06, 2007 10:37 am

Post by PartEleven » Wed Aug 26, 2009 7:00 am

Honestly, with a question like this you aren't going to get many answers other than half-hearted speculations or anecdotal stories. Performance and silence are somewhat opposites, in that if you're optimizing for one then the other will suffer. You need to decide for yourself what level of optimization you will settle for each as no one else can give you an absolute answer. To do that would require someone to test nearly every possible computer configuration using some kind of metric like performance per dB and then graph that on a scale. That's a lot of work and even then would only apply to the case/cooling system that was used in the test.

hypnos
Posts: 22
Joined: Thu Jan 22, 2004 5:54 pm

Post by hypnos » Fri Aug 28, 2009 1:23 pm

TheAtomicKid wrote:I cool a Q6600 passively in my main rig.
What are your core temps at idle and under load (what is ambient with these temps)? What MB are you using?

I tried to cool a 9650 passively with a Ninja 2000 but finally gave in and used the fan they include with the Ninja.

Wayne Redpath
Posts: 104
Joined: Wed Jul 29, 2009 7:42 am
Location: Calgary, Alberta, Canada

Post by Wayne Redpath » Fri Aug 28, 2009 9:27 pm

"it wold receive some assisted air movement"

I can't exactly answer your question but here is my quiet system:

I use only one fan in the upper chamber of my P180 case. The top fan position is blocked off and air enters through the filter on the lower front and exits through the upper rear fan position. A 1150 rpm Scythe Gentle Typhoon does double duty by both getting the heat away from the CPU and moving room air through the chassis. The fan is mounted on the Scythe Ninja on the side adjacent to the rear chassis fan location and blowing towards the rear of the chassis. A 2.5 cm (1 inch) duct made out of a 120mm fan with the guts cut out is mounted on the rear chassis fan location. The CPU fan and the duct align well enough for most of the air to exit the chassis. The fan is connected to the CPU fan connector and the ASUS fan control is set for DC fan type and Silent profile. When the system is in idle the CPU fan runs at 700 rpm and speeds up to 1200 rpm at full load. Idle temperature is around 20'C above ambient and full load temperature is 45'C above ambient.

This cooling setup compared to normal configurations reduces noise in these ways:
=> There is only one fan making noise.
=> The Scythe Gentle Typhoon has the most non-annoying noise signature that I know of.
=> The fan makes less noise sucking air from the heatsink than blasting turbulent air at the heatsink.
=> The less turbulent air from the Gentle Typhoon has time to moderate before hitting that nasty cheap steel stammping rear grill.

This computer is almost silent during the day and when things quiet down in the late evening I can here a gentle, quiet whirr.

swoody
Posts: 48
Joined: Mon Mar 16, 2009 12:43 am
Location: Chicago, USA

Post by swoody » Sat Aug 29, 2009 10:42 am

Wayne, thanks for your setup details :)

That's similar to how I was hoping to run mine. I was thinking about running the hr-01, though, and having the fan just mounted on the case itself, and running it off the CPU header for PWM control, just like you did. Of course I always cut out the steel mesh over my rear fans, but that's a minor detail.

swoody
Posts: 48
Joined: Mon Mar 16, 2009 12:43 am
Location: Chicago, USA

Post by swoody » Sat Aug 29, 2009 10:43 am

Wayne - Also, are you running a fanless PSU? You had made a note that there was only one fan in the case, but I'm not sure if you excluding the PSU fan, or if yours is fanless. Thanks again!

Wayne Redpath
Posts: 104
Joined: Wed Jul 29, 2009 7:42 am
Location: Calgary, Alberta, Canada

Post by Wayne Redpath » Sat Aug 29, 2009 11:45 am

There is an 800rpm Scythe S-FLEX in the lower chamber between the silent PS and the 2 FXD's. The advantage is that the fan noise is inside and not at the edge of the case.

If I was using a "hotter" CPU and/or lived in a warmer region then I would use the 1850rpm Scythe Gentle Typhoon.

My Quiet System: Antec P180 spcr_edition, Antec Phantom 500, ASUS P5WDG2 WS PRO, Pentium Dual Core E2220, Scythe NINJA, Sapphire HD 3850, 2 of WD RE 500, Wireless N-type Lan card, Satellite TV card.

electrodacus
-- Vendor --
Posts: 372
Joined: Sun Jul 12, 2009 10:30 am
Location: Canada
Contact:

Post by electrodacus » Sun Aug 30, 2009 11:49 am

See this viewtopic.php?t=55084
Is a quad core Q8400S that can be run passiveley with a AXP-140 heatsink and the CPU at 2GHZ and 0.925V. This will be almost as powerful as a dual core at 4GHz if your application is able to use multi thread.
And yes this is a 65W TDP CPU but the 95W TDP will do the same if undervolted it will not be more than 1 or 2W difference so do not pay extra for the 65W variant.

For now the most power efficient CPU's are the 45nm quad core you want as many cores as possible with lo voltage and for now quad core are on the top of this list a dual core will take more power for the same level of performance and core i7 is not power efficient.

hypnos
Posts: 22
Joined: Thu Jan 22, 2004 5:54 pm

Post by hypnos » Mon Aug 31, 2009 10:32 am

Wayne Redpath wrote:Idle temperature is around 20'C above ambient and full load temperature is 45'C above ambient.

Are those temps core or tcase?

nomoon
Posts: 201
Joined: Thu Apr 14, 2005 8:35 pm
Location: Allen, TX US
Contact:

Post by nomoon » Mon Aug 31, 2009 11:30 am

For what it's worth, I suspect that passively cooling the CPU may not be quietest solution. See this thread.

Edit: I corrected the link.

Jason
Last edited by nomoon on Thu Sep 03, 2009 5:01 am, edited 1 time in total.

Wayne Redpath
Posts: 104
Joined: Wed Jul 29, 2009 7:42 am
Location: Calgary, Alberta, Canada

Post by Wayne Redpath » Mon Aug 31, 2009 3:25 pm

hypnos wrote:
Are those temps core or tcase?
Those are CPU temperatures reported by ASUS Probe II.

hypnos
Posts: 22
Joined: Thu Jan 22, 2004 5:54 pm

Post by hypnos » Mon Aug 31, 2009 6:35 pm

Wayne Redpath wrote:Those are CPU temperatures reported by ASUS Probe II.
That would be tcase. If you have a chance would you run coretemp, speedfan, or one of the other core temp monitors to see what you get?

Olle P
Posts: 671
Joined: Tue Nov 04, 2008 6:03 am
Location: Sweden

Post by Olle P » Wed Sep 02, 2009 3:55 am

From a theoretical perspective I see no applicable upper limit for a completely fan-less computer, provided the parts are custom designed.

Just pick inspiration from the Zalman TNN case and then extrapolate from there. (More spread of the heatpipes, larger and more elaborate heatsinks, etc.)

Cheers
Olle

swoody
Posts: 48
Joined: Mon Mar 16, 2009 12:43 am
Location: Chicago, USA

Post by swoody » Wed Sep 02, 2009 3:47 pm

nomoon wrote:For what it's worth, I suspect that passively cooling the CPU may not be quietest solution. See this thread.

Jason
That's this thread :)

nomoon
Posts: 201
Joined: Thu Apr 14, 2005 8:35 pm
Location: Allen, TX US
Contact:

Post by nomoon » Thu Sep 03, 2009 5:02 am

swoody wrote:
nomoon wrote:For what it's worth, I suspect that passively cooling the CPU may not be quietest solution. See this thread.

Jason
That's this thread :)
Acck! Here's the correct thread.

Jason

Rebellious
Posts: 322
Joined: Sun Dec 09, 2007 12:53 pm
Location: EU, USA

Post by Rebellious » Sat Sep 05, 2009 11:37 am

I've run a 125W CPU fanless

viewtopic.php?t=51531

I think 140W CPU is also doable with the right case & heatsink. The only problem I've noticed is that by moving more air through the case you're also accumulating more dust.



//

electrodacus
-- Vendor --
Posts: 372
Joined: Sun Jul 12, 2009 10:30 am
Location: Canada
Contact:

Post by electrodacus » Sat Sep 05, 2009 11:44 am

Rebellious wrote:I've run a 125W CPU fanless

viewtopic.php?t=51531

I think 140W CPU is also doable with the right case & heatsink. The only problem I've noticed is that by moving more air through the case you're also accumulating more dust.



//
Nice build but is not fanless

Rebellious
Posts: 322
Joined: Sun Dec 09, 2007 12:53 pm
Location: EU, USA

Post by Rebellious » Sun Sep 06, 2009 4:46 am

electrodacus wrote:
Rebellious wrote:I've run a 125W CPU fanless

viewtopic.php?t=51531

I think 140W CPU is also doable with the right case & heatsink. The only problem I've noticed is that by moving more air through the case you're also accumulating more dust.



//
Nice build but is not fanless

My response was to the original post, "powerful CPU you can cool passively... with 120mm case fan".

FartingBob
Patron of SPCR
Posts: 744
Joined: Tue Mar 04, 2008 4:05 am
Location: London
Contact:

Post by FartingBob » Sun Sep 06, 2009 5:04 am

I have a Scythe ninja 2 w/o fan cooling my Q9400 in a Antec SOLO. Scythe slipstream 1200rpm fan on the exhaust running at 5v (fanmate). I also have opened up the optical drive bays and put a 800rpm fan there in a kama bay. It aims right at the ninja and means that its not just getting air thats already warmed up by HDD's, GPU and northbridge.

The CPU idles at around 40c (well 1 core does which is always about 4c warmer than the others for some reason, probably uneven thermal paste). Under load (video encoding) it reaches about 60c, or if i turn up the exhaust fan to its rated speed i get about 54c.
You could easily replace the Q9400 with a Q9550 or any of the low power Q9xxx series. I have no idea about the i7's.

electrodacus
-- Vendor --
Posts: 372
Joined: Sun Jul 12, 2009 10:30 am
Location: Canada
Contact:

Post by electrodacus » Sun Sep 06, 2009 9:51 am

I will not consider fanless a CPU that is in a case with one, two or even 4 case fan's I think is a better solution to have less case fan (or none) and use a low speed CPU fan it will be more efficient.

Post Reply