I replaced the whining chipset fan on my A8N-SLI last night with the heatpipe ordered from the ASUS parts store. Installation was relatively straightforward after removing the mobo from the case:
1. Remove the old chipset fan and the MOSFET heatsink. This is accomplished through squeezable pins which are accessible from the back of the mobo. I had to clip the chipset fan pins off with a small pair of flat-nosed wire clippers (carefully), but the MOSFET pins squeezed right out. Note that pushing on the pin from the other side (the "right" side) of the mobo while squeezing may help by providing clearance.
2. Put the chipset fan aside. Marvel at its cheapness. Repeat for MOSFET heatsink. Note that there appears only to be a rubbery strip of something (bearing no resemblance to any kind of thermal interface material I have ever come across) on its bottom.
3. Clean off the pink, and probably now-hardened TIM from the chipset chip. This may take a while with 91% isopropanol. If you have access to acetone, that may work better. A wooden toothpick can be handy for scraping off the really stubbon stuff, and lens paper (Kimwipes are great) is ideal for actual cleaning/wiping.
4. Clean off the pre-applied TIM from the heatpipe's heatsink areas. Replace with a layer of Ceramique. I applied a generous layer of Ceramique to the heatsink regions with a plastic-gloved hand. I then wiped off all of the TIM with lens paper, leaving only a thin haze behind.
5. Put a SMALL drop of TIM on a gloved finger and spread it in a THIN later over the exposed chipset chip. I did not put any TIM on the MOSFETS, relying only on the residual TIM on the MOSFET heatsink from step #4. These were just too small to risk any spillover; I suppose one could use a cotton swab.
6. Install the heatpipe. Note that this step is made much easier if one rests the mobo on an anti-static bag over a cushiony material. I pushed the pins through the heatsink covering the chipset first. This was uneventful. The MOSFET heatsink required a bit of coaxing to align the holes, but was nothing too difficult. Compatability appears to be spot-on.
That's it!
As A8N-SLI owners have found, the mobo temp reading is not the chipset reading. Therefore, I have no idea what my chipset's temp was with the fan. I did notice that neither the MOSFET heatsink nor the fan's aluminum covering got particularly hot, which would indicate that either the chipset fan was very effective/MOSFETS did not heat up much, or that contact was suboptimal.
Last night, while everything was out of the case, I installed the CoolerMaster Aerogate III fan controller/temp monitor that I bought some time ago. I inserted a flat temperature sensor as far as I could under the heatpipe's chipset heatsink and thus my chipset temp readings come from that probe. The probes do appear to be relatively accurate from measuring my other components.
Chipset temperature when the computer has been on for 15 minutes at idle:
53-55C with an ambient case temp of 29-30C and a room temperature of 24-25C.
Temps do not heat up whether I place the system under full load (Prime 95) or OC (250FSB). The heatsink over the chipset is definitely hot, and certainly feels like it is over 50C. I cannot keep my finger on it for more than 5 seconds without pain (and my fingertips are pretty well calloused). The MOSFET heatsink is notably hotter than before (I would estimate 45C), but I could touch that indefintely without pain. The heatpipe itself is hot as well.
As an experiment, I physically placed a Zalman passive chipset heatsink on the chipset heatsink. No TIM or anything- just plain metal-to-metal held in place by my hand. This dropped the temps down by 3-4C within two minutes. Running the system with the side panel off dropped it another 4-5C. Admittedly, my case has pretty poor airflow (Wavemaster), although I have cut a 120mm hole in the side panel over the CPU for passive intake. I also figured out a way to soft mount 92mm fans in the front for intake, but only had one 92mm fan on hand yesterday, so that may make another 1-2C difference. Installing a 120mm fan on the side as intake made no difference (but did lower CPU temps another 2C). Blowing air directly over the MOSFET did not seem to make much of a difference. I currently have a 92mm fan on the stock 4-heatpipe Opteron/X2 heatsink, so there is a bit of spillover air to begin with.
I Primed the system for 4h last night, and this morning everything looked OK (no OC; I do not OC except for testing purposes). Chipset temps are very stable around 53-55C, idle or full load. No other system temps have changed with the possible exception of the "motherboard/system" temp reading, which has gone from 37C to 35C. I do not know how significant, if at all, this is. I also have no idea where the temp sensor is. For all I know, I could have bumped it when I had the mobo out of the case.
I really wish I had northbridge temp readings with the old chipset fan only. Considering how hot the heatpipe gets now, I really doubt that the old fan was making good contact. I am almost positive the old MOSFET heatsink was not doing much. As far as I know, 55C is OK, as the chipset is rated to 90C, IIRC. I am not thrilled with this temp, though, and the perfectionist in me is looking for ways to further reduce the reading. I am considering attaching the Zalman (it is the smaller 32mm square) passive heatsink on top of the heatpipe chipset heatsink with thermal tape.
I will update when I get my thermal tape and 92mm fan. Hope others who install can share their results.