Passive CPU cooling... what to chose?

Dirge · Post by **Dirge** » Thu Aug 05, 2004 5:03 pm

Could anyone give me an idea of the maximum power dissipation that can be safely removed by a quality heatsink.

My aim it to build a silent pc that requires no cpu or case fans. I would consider integrating a fanless psu if it did not generate too much heat.

Speed is not a huge issue as long as I can continue to use office software and browse the net comfortably.

sthayashi · Post by **sthayashi** » Thu Aug 05, 2004 9:18 pm

Via processors can pretty much be run silently.

Dirge · Post by **Dirge** » Thu Aug 05, 2004 10:02 pm

sthayashi are you talking about the mini-itx boards via makes? Can the heatsink be replaced as i think they have fans on them.

I know the Eden M6000 is fanless but from what i read it is also very hot and requires a case fan.

My aim is to run with no cpu or case fans.

MonsterMac · Post by **MonsterMac** » Thu Aug 05, 2004 10:09 pm

that's quite the goal, but i'm sure with a little hard work it can be done. good luck to ya, be sure to post it in the gallery once you're done with it

Post by **MikeC** » Thu Aug 05, 2004 10:11 pm

Could anyone give me an idea of the maximum power dissipation that can be safely removed by a quality heatsink.

Dirge, that's not a question anyone can answer -- at least not without so many conditions and qualifiers that in the end it would be a useless answer. I can honestly say it can range from under 10W to over 100W -- just depends on how far you want to go!

If you are talking about an EPIA 6000, those things come w/o a fan and can be run w/o any fan in the case -- though it has to be a pretty open/good case. Yes it will run hot but the C3 cores seem to do fine at very high temps. The eOtanashi / Scythe fanless EPIA-m HS/case (with flat heatpipe) that I reviewed a while ago does very well. Combine it w/a quiet notebook drive and you got yourself a <20 dBA/1m system.

sthayashi · Post by **sthayashi** » Thu Aug 05, 2004 10:12 pm

Yes, I am.

The Eden M10000 can be run fanless as well. Look at the Mappit review. Or check out their website.

Dirge · Post by **Dirge** » Thu Aug 05, 2004 10:46 pm

How difficult is it to attach a new heatsink to a mini-itx board?? For instance do they don't seem to have a socket.

I would be a little hesitant to rely on thermal epoxy alone.

Post by **MikeC** » Thu Aug 05, 2004 10:58 pm

Dirge wrote:How difficult is it to attach a new heatsink to a mini-itx board?? For instance do they don't seem to have a socket.

I would be a little hesitant to rely on thermal epoxy alone.

If you are not real handy, forget about homebrew solutions. There are only 2 little holes for mounting, and it uses spring loaded plastic push pins, the kind for low end VGA cards and NB heatsinks. There's no way to get any standard CPU HS on this board.

Dirge · Post by **Dirge** » Thu Aug 05, 2004 11:22 pm

MikeC you say the Via C3 can tolerate high temperatures, do you have any idea what the max temp is.

I would like to know what temperature range it can operate at safely. I was intrigued to see reviews on this site where the temps exceeded 70c at load. Can it go much higher than that for extended periods of time?

the_smell · Post by **the_smell** » Thu Aug 05, 2004 11:31 pm

You coule also try getting a via C3 chip and a socket 370 motherboard, you should be able to passive cool (my server is not passive as the psu has a fan, but with a fresh air duct it would be easy to passively cool the CPU).
Alternatively you could get a mobile athlon or P4 and underclock and undervolt, then you'll have a much more powerful system than what could be achieved with current via cpus.

Dirge · Post by **Dirge** » Thu Aug 05, 2004 11:37 pm

the_smell you make a good point. I have also considered undervolting a more powerful cpu to achieve lowered power dissipation.

My problem is I don't know how much heat a good heatsink can dissipate withought the need for a fan. I suspect it might be in the range of 10-20w but would like to hear from you experts.

Post by **MikeC** » Thu Aug 05, 2004 11:44 pm

Not sure what max temp is, but there used to be a video at the VIA site that showed a C3 system w/o HS... Ah found the page: http://www.via.com.tw/en/Products/movie.jsp

On that page, look for Beat the Heat: What happens when you remove the heatsink and fan from a VIA C3â„¢ processor?

All this has been discussed in great detail before. Try a search for C3. One of threads that will show up is:

Fanles VIA C3 Nehemiah 1200Mhz machine done! -- http://forums.silentpcreview.com/viewtopic.php?t=9704

Tigr · Post by **Tigr** » Fri Aug 06, 2004 12:06 am

Well, you can safely cool a Mobile XP processor running between 500 MHz and 1 GHz with a Zalman "flower" (CNPS-6000, wasn't it?). The max power of the CPU will depend on your case airflow, YMMV.

the_smell · Post by **the_smell** » Fri Aug 06, 2004 12:07 am

I don't have any experience in the good old mobile cpus, but I think generally people aim to get under 20w to passively cool with a good heatsink, although often this is with a little case airflow. With heat pipes and big heatsinks you can passively cool just about anything:
http://www.silentpcreview.com/modules.p ... 114&page=1
Also see the zalman TNN 500A monster.

Probably what would be easiest to get a powerful passive system is using a P4-M with a heatlane zen for a cooler, or any P4-M/Athlon-M with a big zalman or thermalright heatsink. But a passive via system would probably be a little cheaper.

Edit: I am no expert, I leave that for Mike C and friends!

smilingcrow · Post by **smilingcrow** » Sat Aug 07, 2004 8:20 am

One important point is to decide what is the maximum case temperature that you are happy to live with?
Itâ€™s not so difficult to adequately passively cool an under-clocked and under-volted Athlon XP, Athlon 64or possibly even a Northwood, but the case temps might get uncomfortably high.
That I find is usually my critical point, as Iâ€™m more concerned with damaging other system components than the CPU, especially with all the thermal safeguards on modern processors.

The only system that Iâ€™ve ever passively cooled was a Celeron 600 under-volted to 1.3 from 1.5V. That equates to about 9W from the standard 12.6W

Copper · Post by **Copper** » Sun Aug 08, 2004 6:53 pm

I've been able to passively cool about 20 watts. In the picture below you can see my latest ghetto setup. The boards are out of Shuttle Zens and use external brick PSU's that are hidden out of view. In this configuration I'm able to run dual instances of CPUburn on a 3.0C @ 2.0ghz with a reported temp of 66C.

Previously, I was able to get the assembled system to run dual instances of CPUburn on a 3.0C at 1.5ghz with a reported temp of 54C. It was necessary to cut vent holes in the case for this to work though. Otherwise the inside of the case became an oven and just about everything, including the CPU, overheated. You can see the vent holes in the top Zen in the pic below: (I ran it passive before I got the Reserator)

Two points of interest that I would add. Even at 1.5ghz, the P4 will blow VIA out of the water performance wise. And, if you do get completely passive be prepaired to address your hard drive. It will drive you nuts. A notebook drive wrapped in foam and stuffed in a Smart Drive works outstandingly.

One drawback is that you are either going to have a ghetto setup, get a drill and jigsaw after your case cover, or find a heatsink/case combo like the Mappit (VIA) or Zalman (big bucks). The results cannot be argued with, though.

Dirge · Post by **Dirge** » Sun Aug 08, 2004 11:31 pm

Wow Copper what an incredible setup, I am very impressed

Can one buy a similar heatpipe cpu cooler through retail?

Currently I am running an AthlonXP 1800+ which I am sure can be underclocked/undervolted to dissipate between 10-20w of heat. Could someone recommend a good heatsink that could dissipate between 10-20w and is not too pricey?

If not then maybe I could spring for a VIA Mini-Itx board after some saving.

Copper · Post by **Copper** » Mon Aug 09, 2004 3:59 am

You can get the ICE cooler, but it's for P4's.

http://us.shuttle.com/specs_access.asp?pro_id=349

It does fit in any standard P4 socket but you need to be sure the heat pipes have clearance.

silvervarg · Post by **silvervarg** » Wed Aug 11, 2004 6:45 am

I agree with Copper that somewhere in the 20W region is what you can cool passively with a reasonable amount of work. With lots of work and money you can get to something like the TNN-500 that is big, ugly and expensive, but can cool 150W passively.
Btw, congratulations to a great passive setup Copper.

The cheapest and esiest way is to get a VIA C3 CPU. Either you get the 600MHZ version or the 1.0GHZ or 1.2GHz Nehemiah core.

A faster option is the Athlon XP-M that can be underclocked and undervolted to be passively cooled. I have an old unlocked Athlon XP 2500+ (not mobile) that I runn passively at XP 1500 speed, and this seems to be the top speed that someone manages to run passively. I would say that this is equal to Coppers system, with a few minor differences. He uses expensive P4 3.0C heavilly underclocked. I run a dirt cheap CPU inside a computer case.
And I managed to pull it off 1/2 year before Copper...

The biggest challenge isn't the CPU (it is just a matter of how low you must underclock). The two biggest problems are PSU and HDD.

To get ridd of the PSU noise you have 3 options:
1. Buy a fanless ATX PSU. Most of them require that you have case fans, and that kind of defeats the purpouse of a fanless PSU. They are also rather expensive.
2. Mod a PSU to become fanless. Trodas took this aproach, and did a great job. This does require quite a lot of skill, so it is not for everyone.
3. Buy a brick PSU and DC/DC board. These are normally used in laptops and miniITX systems. Power is very limited, so you will be on a thight power-budget. You need to start counting every watt you will need for all the devices in the system. Most tricky is how much is needed for HDD and optical drives during spin up. It is very hard to find a decent brick PSU package. So far I have not succeded in this matter.

HDD noise:
1. Be content with just dampening the HDD noise. Either with suspending and using isolation materials (the approach I took) or using some good HDD enclosures (the approach Copper took).
2. Run without HDD. A few options are available. Boot over network and mount a network drive. Use a solid state drive. Put in huge amount of RAM, setup a RAM drive and use a HDD during boot only and have a small solid state drive/ USB memory/ ... for user data only.

Also consider using laptop drives. Smaller (both physical and storage capacity), slower, less noisy, use less power and slightly more expensive.

Perhaps have a glance at turn key solutions like Hush miniITX (still needs to fix noise from HDD).

Solid state drives are very expensive. Some cheap 800MB drives can be found at ebay. This works with a small margin for win98, but it is too small to manage an Windows XP installation. Could probably manage a minimal Linux installation.

silvervarg · Post by **silvervarg** » Wed Aug 11, 2004 8:52 am

I just found out that DC2DC has restarted its webshop, and it seems that they have stopped selling through vendors. They are the only company that I have found so far that seems to sell PSU kits (brick+DC/DC board) that can handle ATX boards. Problem is that shipping to Europe is quite expensive USD 67.80.
Considering that a PSU kit is around USD 80 the shipping almost doubles the cost.
Anyone from sweden interested in a group buy?

I believe that this is the best solution to a fanless system. With the 120W kit (that actually can take 120W on 12V alone) it should not be any problems to run most normal computers with the PSU kit.
One slight problem is that the power cord is for US only, but the brick handles 110-240 v fine.

ist.martin · Post by **ist.martin** » Wed Aug 11, 2004 9:50 am

Dirge wrote: Speed is not a huge issue as long as I can continue to use office software and browse the net comfortably.

Check out Mike's review of the Scythe Otanashi case that is used for VIA M10000 in a fanless configuration. I believe the VIA's are about 15-17 W and can be safely run to 70*C.

I have been using mine for a couple of months now - with a $50 800MB flash IDE drive and 98SE + OE. I have about 10 web windows open constantly, and have no performance problems.

It has been really warm here (high 20's C), and I have had no problems with the system, in spite of BIOS readings of 72*C on the CPU)

If you go totally silent (Flash IDE HD), for Office, you need to use an external USB HD, as there won't be enough space on the 800MB drive for Office.

the_smell · Post by **the_smell** » Wed Aug 11, 2004 2:13 pm

mini itx sell a few brick passive PSUs, but they don't recommend using them with full atx boards but it should be able to cope with a low power system:
http://www.mini-itx.com/store/default.asp?c=10#p1806
They don't look any cheaper than the importing option you gave silvervarg

aidanjm2004 · Post by **aidanjm2004** » Wed Aug 11, 2004 4:35 pm

Copper wrote:One drawback is that you are either going to have a ghetto setup, get a drill and jigsaw after your case cover, or find a heatsink/case combo like the Mappit (VIA) or Zalman (big bucks). The results cannot be argued with, though.

Aren't those cute little Zen beasts angry with you, though, for cruelly ripping them open and displaying their innards on a shelf?

pangit · Post by **pangit** » Wed Aug 11, 2004 6:38 pm

Cooling VIA C3 processors passively is dead easy. You can see one I built for my Dad here using a C3 800MHz, an old generic Athlon heatsink, and good airflow. The only fan in the entire system is a very quiet one in the PSU. The Weetabix shroud in the pics is not even necessary.

It's not the fastest machine in the world, but it runs WinXP and office/browsing applications no problems, which is all it will ever be used for.

Dirge · Post by **Dirge** » Thu Aug 12, 2004 11:34 pm

silvervarg wrote:A faster option is the Athlon XP-M that can be underclocked and undervolted to be passively cooled. I have an old unlocked Athlon XP 2500+ (not mobile) that I runn passively at XP 1500 speed, and this seems to be the top speed that someone manages to run passively.

Thanks for your reply silvervarg I found it very informative. I was wondering what kind of setup you used to achieve a passively cooled cpu at XP 1500 speeds?

What vcore and multiplyer settings are you using? Could you also tell me about your choice of heatsink?

I think underclocking my XP 1800+ in a similar fashion would give me better performance than a C3

silvervarg · Post by **silvervarg** » Fri Aug 13, 2004 12:28 am

Dirge:
I was wondering what kind of setup you used to achieve a passively cooled cpu at XP 1500 speeds?

What vcore and multiplyer settings are you using? Could you also tell me about your choice of heatsink?

I think underclocking my XP 1800+ in a similar fashion would give me better performance than a C3

For most information I suggest that you read my webpage about the build.
http://www.silvervarg.nu/henrik/dator/c ... build.html
Also see my signature.

I have changed the multiplier and FSB a few times to try different settings. Since I run an Abit NF7-M board I can change FSB on the fly, but changing multiplier requires a reboot. Due to this using a slow FSB is a bit interesting, since I can increase FSB without rebooting when I want more power.
I normally run with 1.175vcore, always rock solid stability.

Note that the XP 2500+ has the Barton core, but the XP 1800+ has the throughbreed core, and that can make some difference.
The general idea that with a little underclock you can lower the vcore a lot and cut most of the heat will still work.
You typically want to lower the multiplier quite a bit to keep speed up on the rest of the system, so using a CPU that is not multiplier locked is very important.

Please let us know how the underclocking works out.

A C3 1.0GHz will have similar performance to a XP ~700+ so you can do quite a lot of underclocking and still keep more speed.

Copper · Post by **Copper** » Fri Aug 13, 2004 7:40 pm

aidanjm2004 wrote:Aren't those cute little Zen beasts angry with you, though, for cruelly ripping them open and displaying their innards on a shelf?

It just occured to me that the design of the ICE cooler begged to be put in that configuration. My temps dropped 6C just by pulling the board and screwing it to the side of the shelf. After seeing the temps drop I felt extremely compelled to raise the clock

I got it from 1.5 ghz passive all the way up to 2 ghz passive.

The board on the right and closest to the camera has a 3.0E prescott under it running passive at 1.545 ghz with a .9500 Vcore, a testiment to the value of the underclock.

Dirge · Post by **Dirge** » Sat Aug 14, 2004 4:04 am

Sounds like the I.C.E. Tech Heat-Pipe is perfect for passively cooling P4's.

If Intel ever releases a desktop version of the Pentium-M I would love to see it under one of these coolers.

Passive CPU cooling... what to chose?

Passive CPU cooling... what to chose?

Re: Passive CPU cooling... what to chose?