Goff said:
You are correct concerning the CPU Heatsink/fan. The board is an ASUS
A8N-SLI , NForce-4 chipset, one 6600GT, and an AMD 3700+ CPU.
ASUS PC Probe currently reads, at idle, and without "Cool 'n Quiet;
CPU Temp - 29C/84F
MB Temp - 35C/95F
Ambient temp is 65F inside.
Possible replacements:
1) Go to the estore.asus.com and get an exact replacement. Only
an option for residents of the USA.
http://estore.asus.com/shop/item.asp?itemid=231&catid=134
("Out of stock until first week of April.")
2) Thermalright HR-05-SLI Copper Heatsinks only - Retail
http://www.newegg.com/Product/ProductReview.aspx?Item=N82E16835109131
That is a heatpipe based cooler, intended for use with Northbridge
chips. The "SLI" designation comes from the ability to orient the
fin assembly, so it doesn't bump into a video card. Thermalright
makes a second model, with different mechanical details.
The cooler could benefit from having a fan mounted next to it.
If the chipset was still too hot, more air flow over the fins
would help.
Since the clip isn't apparently very good, you may want to
visit the hardware store, and improve the design a bit.
3) MCX-159CU
http://www.swiftnets.com/products/mcx159-CU.asp
This is a Northbridge cooler, with an included fan. Fan is 18dBA,
which is below 30dBA or so audibility figure. Swiftech products
usually have nice surface finish on the base of their coolers.
There are no heatpipes in that unit, but yet it is rated
with a theta_R thermal resistance of 1.25C/W. If the chipset
was 20W, that would mean the chip temp would be 35C (case air temp)
plus 1.25*20 = 60C as a rough estimate.
For a cooler like the 159, you'd want to verify the corner to corner
spacing of the mounting holes. The brackets on the 159 have limited
adjustment range, so you pretty well need the standard hole spacing
to be able to use it.
4) I would not recommend the Zalman NB47 or similar 35mm square
passive coolers for a chip like that Nvidia one. The problem is,
the theta_R on those coolers is too poor for comfort. A more
substantial cooler is required. And preferably with some air movement.
On some heatsinks, 200LFM of air, improves cooling performance by a
factor of three, and should not be ignored. As you can see in the
calculation in (3), it still runs pretty hot with a 35mm cooler
without heatpipes.
The HR-05 comes with some thermal paste, and a thin layer should be
applied to the top of the chip, once it has been cleaned with some
isopropyl alcohol. Thermal paste compensates for the unevenness of the
surfaces, and paste is a better conductor of heat, than air. By
displacing any air between the two surfaces, you get better cooling
performance. When the motherboard is manufactured, sometimes they put
a gob of material in there, and too much of it, acts as an insulator.
http://c1.neweggimages.com/NeweggImage/productimage/35-109-131-05.jpg
There are various discussions about fans and cooling for that motherboard,
on the Asus forums. There are too many posts for me to read right now,
and 1418 threads might take me the rest of the day.
http://vip.asus.com/forum/topic.aspx?board_id=1&model=A8N-SLI&SLanguage=en-us
HTH,
Paul