CPU & thermal adhesive

jon · § #1 11-12-2002, 05:04 AM

Hopefuly someone can advise me on this...

I want to replace the heatsink and fan on a VIA C3 800 processor with a fanless heatsink. THe heatsink I found is designed for fanless operation with this processor (C3 Heatsink ).

However, the mounting points on the motherboard do not correspond the those on the heatsink. (The motherboard is the VIA Epia, and has H/S mounts at opposite corners of the CPU).

I therefore need some way of attaching the H/S to the CPU. I'd rather not try drilling the H/S to create new mounts, and was wondering about thermal adhesive.

I read on www.ArcticSilver.com that thermal adhesive is not suitable for use on CPUs. Does anyone know why?

The VIA EPIA-800 platform is equipped with C3-E 800MHz processor, which generates 8.5W at full load. This is pretty minimal compared to modern Athlon processors, so I was hoping that I might get away with it???

Any thoughts?

Thanks,

opofus2002 · § #2 11-12-2002, 08:02 AM

Its safe for cpu , BUT its none removeable so if you epoxy a sink on the chip probably cant be removed from the board.

jon · § #3 11-12-2002, 08:11 AM

Thanks opofus2002. Your help is much appreciated.

I'm not *too* worried about sticking the H/S onto the CPU permanently, as it does say that it is designed for that CPU. (although I am a bit worried - what if I f*(k it up??) - dead mobo & CPU, as they are soldered together on the Epia models.

I guess if you want something a bit special, then you have to take the odd chance here or there.

I want to do this, as with this Mobo, I can use a fanless laptop PSU, and if there is no CPU fan, then there will (hopefully) be no noise at all. Then I'll have a nice PC based appliance for playing music in the lounge and surfing the net. (To replace the existing AMD K6/2 400).

JOn

opofus2002 · § #4 11-12-2002, 02:16 PM

Hey jon is it raining down there? it is in the midlands.

If the chip is soldered in then you lose nothing by permanently fixing the sink on. If its not good enough you can get a quiet low pressure/flow fan and put it on. The rest is up to you....

jon · § #5 11-13-2002, 05:24 AM

Certainly was p!ss!ng down yesterday. Not too bad now.

I got an email back from Arctic Silver, saying that basically, you were absolutely correct in your first reply, and I'm pretty happy about it. Now I can start building a totally silent

800 (or 933) Mhz PC for music and video/Dvd.

Thanks again,

JOn

If yer interested, the letter from Arctic Silver is below:

The reason we do not recommend using the Adhesive to hold a heatsink on a CPU because it is almost impossible to hold the heatsink perfectly flush on the core as the adhesive sets. The core on a modern AMD or Intel PIII CPU is very small and does not contact the center of the heatsink so it is like trying to balance a dictionary on a Pepsi bottle.

Also, once a heatsink is glued to a CPU, the socket release lever cannot be raised so the motherboard, CPU and heatsink are mated forever.

Since the heat spreader on your CPU that contacts the heatsink is much larger than the contact area on the CPUs I mentioned, you actually have a better chance of getting a good interface between the CPU and heatsink. The C3 processors do not produce much heat relative to their large contact area so I would suggest our less expensive ceramic based adhesive, Arctic Alumina Thermal Adhesive.

If you decide to try it, use a very thin layer on the CPU heat spreader only, keep the heatsink flat on the core and apply pressure to the bond for at least an hour or two to allow a good set. Wait at least 6 hours before you use the Computer.

Hope this helps,

opofus2002 · § #6 11-13-2002, 03:48 PM

Its a nice reply, someone thought about it. Let us know the results.

jon · § #7 11-14-2002, 05:05 AM

I will let you know. I have (sort of ) decided to wait for the new updated version of the motherboard I want.

The new version has a 933Mhz CPU instead of 800, and also has better onboard sound and video (which is handy, as there is only one PCI slot, and I need that for a second network card.)

Also waiting for my ordered laptop style PSU.

Ta,

JOn

RavenTai · § #8 11-15-2002, 12:30 AM

This sounds like a good place to try one of those zalman flowers http://www.directron.com/cnps60001.html a little more pricey but I would bet it would give cooler temps, since it is permanent you would hate to find out it does not run cool enough after the fact

jon · § #9 11-15-2002, 05:15 AM

I would definately prefer to use a zalman flower. However, I read this...
http://www.mini-itx.com/hardware.asp#hardware0007
article, and it says that the CPNS6100 does not fit, as there's no socket on the motherboard.

According to Via, (here)

http://www.via.com.tw/en/viac3/C3_silent.jsp

The C3 CPU will work with the Zalman CPNS6100, CPNS6000, and CPNS3000 plus.

If you can suggest a way to fit any of the Zalman heatsinsks, then I would be very grateful. There's a pic of the mobo & CPU here
http://www.mini-itx.com/hardware.asp#hardware0029

You can see that the Heatsink is held on with two pins at opposite corners of the heatsink, rather than the conventional clip across the middle of the heatsink.

Now I think about it, the heatsink I was looking at has the same fitting as the Zalman. Do you think I could just "glue" a zalman flower onto the CPU (using thermal adhesive)?

Alternatively, do you know of any heatsinks that have the mounting points at opposite corners (like the Northbridge/Southbridge (whichever it is) chip on a via motherboard.
I know that Zalman make a passive cooler for the North/Southbridge, but according to Zalman, it doesn't conduct enough heat for my Via C3.

Thanks,

JOn

opofus2002 · § #10 11-15-2002, 12:20 PM

Dam that was a big page!

Have you got the board?
If so measure the hole centers, then we can see if a northbridge cooler will fit. As long as it physicaly fits then thermal epoxy will do (I recomend artic alumina as its not conductive as3 epoxy is and since its a one shot deal I would go with the first).

RavenTai · § #11 11-15-2002, 01:04 PM

Quote:

Originally posted by jon
Now I think about it, the heatsink I was looking at has the same fitting as the Zalman. Do you think I could just "glue" a zalman flower onto the CPU (using thermal adhesive)?
Thanks,

JOn

that is what I was thinking of, looking at that board it is going to be tight there aer so many components arround it everything is so small, the flowers are kinda big that is what makes them such good pasive coolers

jon · § #12 11-18-2002, 04:14 AM

Thanks again guys,

I haven't actually got the board yet, and I am going to wait for the new Epia-M. I spoke to someone at Via, and they reccomended waiting for the new model, as it is designed for digital media.

I think I am going to have to wait until the board comes out in mid december, and measure up the distances.

I have read that the Zalman Northbridge cooler is exactly the right size, and some people have been using one to cool the CPU, apparently with no problems. In fact, I emailed someone at Koolnquiet.co.uk, and he said that he is using one of the northbridge heatsinks on HIS Epia, and it was fine. In fact, some people have just disconnected the fan on the stock heatsink, and reported that it was fine.

I guess I will have to wait and find out.

I'll probably be posting here again mid december with more problems.

JOn