(Update: Pictures shrunk down so hopefully no more complaints about pics being too big.... Thanks Rouvio at the guru3d.com/forums for helping me shrink them down)
The XFX 8800GTS is a great card but runs a bit too hot. There are currently no aftermarket heatsink/fan solution for this card so I decide to modify the existing cooling. I bought a Sapphire x850xt less than a year ago and by applying arctic silver 5, ripping out some platic stickers, and lapping the heatsink surface, the temps went down by 9 deg celcius at idle (forgot what the exact difference was at full load because I ended up buying the Zalman Copper).
For the XFX card I took the following steps at reducing the temps.
1) Unscrew the 8 screws holding the stock heatsink/fan. One is already removed in the picture.
2) Unscrew the restrictive plate at the dvi input end of the card. The small openings on this plate hardly lets out any air. With the restrictive plate in place, most of the air will bounce back instead of being able to flow freely out of the system. This is a major restriction to flow and must be eliminated for proper flow. You can cut it up instead of completely removing it if you are afraid the card might be unstable without the bracket. I did not remove it because I want to preserve my 2-year XFX warranty and also want to keep the card as perfect as can be incase I resell it a few months down the road, which is what I have been doing with all my previous video cards. With the bracket plate remove, I can feel a small breeze of warm air flowing out of the system whereas when I place my hand at the outlet, I couldnt feel anything before the modification (this hand test was at the minimum 25% fan setting)
3) Removing the heatsink/fan from the card will reveal the cheap quality thermal paste/pad used by the factory. For the GPU, it was a dried up flaky gray paste (far from the Arctic Silver 5 quality). For the memory and miscellaneous chips, the manufacturer used white thermal pads which were weaved together by fiber strands. Before taking it out, I observed that the heatsink is not firmly seated on some of the memory surfaces by default, which is why thick fiber woven thermal pads are used to fill the gaps. This is because the eight factory screws removed in step 1 don't go all the way down but instead uses very weak springs attached to the screws to push on the card. This is to prevent the heatsink from sitting lopsided on the gpu (a very common installation error).
4) Rub off the existing thermal compounds and clean it off using rubbing alchol. Carefully finish off the surfaces using alcohol soaked Q-tips to remove any dust or fiber strands.
5) Apply the ultra expensive Arctic Silver 5 thermal paste. Evenly spread the paste over the GPU surface. However for the memory chips and miscellaneous chips, do not spread the paste. Instead, apply dabs at the center to create a pointy cone like form. You can apply very generous amounts of paste on the memory chips but be careful not to apply too much on the smaller chips as you do not want the paste to to touch the metal surfaces (I'm not sure how electrically conductive the paste is)
6) Now slowly and carefully reseat the heatsink/fan on the card by aligning the screw holes. To better seat the heatsink fan against the memory surfaces require a bit more pressure than the weak springs. Use screw washers, or motherboard washers, or even cut out old credit cards and poke a hole through it, will serve well as spacers. Install the spring loaded screws in a criss cross pattern to prevent a lop-sided seating. Do not tighten the bolts down fully the first time, leave a 720deg slack. When all bolts are in, then tighten them down (also in a criss cross fashion). You have to be very careful with this. The first time I did it, the heatsink wasnt seated on some of the memory surfaces as well as I wanted to so I had to take it apart and put it back together. Now everything is seated propery (much better seating than the stock assembly)
7) Thoroughly verify the seating of the heatsink on the chip surfaces one more time. Notice that the seating will not be in perfect contact with the memory chips no matter what. But that is ok, since the arctic silver will transfer heat much better than the stock pads (this is why u can be very generous applying arctic silver on the memory chips). And at least the space between the memory chip surface and heat sink has been greatly reduced from stock.
My test results are as follows. All testing done done at the default 25% fan speed and with a partially open case.
Before mod (ambient temp 10-11deg C):
Idle at underclocked 250mhz core / 200mhz mem, 52deg C
Idle at default 517mhz core/ 792mhz mem, 62deg C
Under Load (Full 3D Mark 2006 stress test) at 625mhz core/ 950mhz mem, 80deg C
After mod (ambient temp 13deg C):
Idle at underclocked 250mhz core / 200mhz mem, 48deg C
Idle at default 517mhz core/ 792mhz mem, 54deg C
Under Load (Full 3D Mark 2006 stress test)at 625mhz core/ 950mhz mem, 71deg C
Conclusions:
From the test results, it is obvious that the modification does reduce temp. It might not be a whole lot of difference and some people might find the hassle of diassembling the card and the cost of the Arctic Silver 5 not worth the few degrees cooler, so it is up to you whether you want to spent the 5 hours or so and $15 in material to get a 10deg or so difference. But keep in mind the ambient temp during the pre-mod test was cooler than the ambient temp during the modded test. And I am sure the temp difference would amplify at higher fan speed settings because the restriction from the bracket plate will exponentionally increase with respect to fan speed. Also I am running a partial open case. I suspect if it was tested in a closed case system, the differences would also be greater because the bracket plate restriction will cause the hot air to cycle back inside the case instead of discharging out of the case.
I have not tried pushing the card to its overclocking limit. I run the card normally at an underclocked 250mhz core and 200mhz mem using AtiTool (way better and easier to use than nvtweak). This significantly reduces temps and prolongs card life, and also consumes less watts. On detecting 3D applications, Atitool will automatically switch to an overclocked 625mhz/950mhz. I havent had problems at this settings before or after the mod. I just cant wait until AtiTool released a new version that allows automatic fan speed settings that changes with temperature for the 8800 series. I used to use that feature for my ATI x850xt and it was awesome!