NightWalker's C90S 8600m GT 512MB "Dual Heatsink" mod.

I take NO responsibility for any damage/harm/whatever if you choose to follow this guide! Proceed at your own risk. Results are not guaranteed and I'm only posting this in an attempt to help fellow C90S users deal with the lack of cooling for our 8600M GT.

As some of you may know, the 512MB version of the 8600m GT on the C90S has absolutely no heatsink or cooling for the bottom four memory modules.

I've thought about making a heatsink for awhile but couldn't figure out exactly what to use. I tried cutting out four copper rectangles and using adhesive to mount them to the memory modules, but later decided against this. After a little testing I think I've found a relatively easy mod that seems to work at cooling these memory modules. I made a short guide if anyone else is interested in giving this a shot.

Parts needed:

Arctic Silver 5 (optional)
Small tip screwdrivers (Flathead and Phillips)
Isopropyl rubbing alcohol (91% or better preferred)
4 small thermal pads
2 small notebook/laptop case screws
Sandpaper
Dremel or other small grinder and various cutting bits
Spare 8600m GT upper "heatsink". Not to be confused with the C90S heatsink.

The guide:

OK, so basically what we are doing is taking a spare upper 8600m GT heatsink and using it to cool the bottom four memory modules just like it does for the top. I'm not talking about the actual C90S GPU heatsink, I am referring to the small "heatsink" or "heat spreader" on the actual card itself. If you are still confused as to what I am talking about here is a picture...



Step 1 (optional)

Start by removing the 8600m GT card itself from the computer. I won't go into great detail on this part because it's a very simple thing to do. Next you have the option of removing the upper 8600m GT heatsink and replacing the stock thermal interface material on the core with Arctic Silver 5. Here is a picture with the heatsink off...



If you are already doing this mod I suggest you take the few extra minutes to do this. When you are done with this reattach the upper heatsink and thermal pads. Next up is modding the spare 8600m GT heastink for use on the bottom 4 memory modules.

Step 2

Unfortunately, we can't just take a spare heatsink and attach it to the bottom memory modules without some modification. We are going to have to grind a few things off to make it work. Below is the same picture with the areas that need to be ground down flat with the rest of the surface circled in red and the areas that need to be ground off completely circled in blue...



The areas circled in red need to be ground down flat with the rest of the surface because if they are not, they will keep the heatsink elevated and the thermal pads will not be able to reach the memory modules. IMPORTANT: The areas circled in blue need to be ground off COMPLETELY because these "ears" will touch the MXM connector itself and could cause a short as well as misaligning the thermal pads during installation.

When you are done you should have something resembling this:



The two "ears" that needed to be ground off and the areas that needed to be ground down flat have been. Don't worry about sanding the heatsink smooth, only the four elevated rectangles are actually going to come in contact with the thermal pads. Just make sure to sand down any sharp edges. Next step is to clean and prep.

Step 3

OK, now that you have preformed the necessary mods to the spare heatsink it's time to clean it up and get it ready for installation. Rub alcohol all over it and make sure to get any grease and shavings off it. When it's done drying out grab your thermal pads and your 8600m GT card and get ready for the installation!

Step 4

This part is a little tricky and I'll do my best to explain the process. Unless you decide to use an adhesive of some sort, the heatsink will not actually be mounted to the bottom of the 8600m GT until you reinstall and screw down the card. Confused? Read on...

Start off by placing the thermal pads on the bottom four 8600m GT memory modules and then placing the modified heatsink on top of the pads. Press firmly, but not to hard. With any luck, the pads should hold the heatsink on a little. Now, while holding the lower heatsink to keep it from falling off, install the 8600m GT.

At this point you might be able to see how the heatsink is going to be permanently mounted. Basically, now that the card has been installed, all you have to do is screw the 8600m GT back down and this will apply the necessary pressure to secure the lower heatsink.

However, there is one more catch. To make this work the stock two screws that are originally used to secure the 8600m GT down won't work. The stock screws are a little too short so you will need to grab two more screws just like the stock ones, but slightly bigger.

Also, when you are screwing the card down BE CAREFUL not to screw the card down TOO much! Because of the additional heatsink at the bottom of the 8600m GT the card will rest at an angle a little. You don't want to screw the card down too much and break it!

When everything is done you now should have something that looks like this:






As you can see from the 2nd picture, this mod not only gives the bottom four memory modules a cooler, it also places that cooler directly on top of the copper pipe that leads to the C90S GPU heatsink.

So at this point in time, after reading this entire guide, I'm sure you are awaiting either an amazing 3DMark06 score, or an 8600m GT card that doesn't get higher then 60 degrees Celsius under load. Well... so far, in my limited testing, this mod doesn't do either. My temps under load have seemed to go down a few degrees, but nothing drastic.

What this mod DOES do is provide proper cooling to the bottom four memory modules, which in turn, also allows me to achieve a much higher stable overclock on the memory then I have previously.

I have only ran one 3DMark06 test and that was with the 174.16 drivers with the clocks at 550/1100/475. Before this mod I could only go to 425 on the memory without crashing. I have also played a few hours of COD4 to make sure it was in fact stable. So far so good.

I will continue testing with 3DMark06 and post the new limits of my card with this mod and also the scores. Keep in mind though, each card has it's only limits and various drivers will also change your scores. I can attest to the difference this mod makes solely on the fact that it can finally overclock higher then 425 for me. I have yet to find the maximum I am able to overclock the memory to but I will continue to keep testing.

Well, that's all there is to this guide. If you do in fact give it a try, go slowly and be careful. Also, this is just how I decided to do it. The basic idea of using a spare heatsink for the memory modules is what makes this work. However, other people might decide to change a few things, such as using adhesive to permanently "fix" the heatsink to the bottom memory modules.

If you use this guide please post on this thread and also share your results with everyone!

 

This is a very good mod and write up. I wanted to do this almost exact mod but with a copper sheet from lowes. I was inspired by the pictures of the way the heatsinks are in the upcoming c90p with the heatsinks under and above the card. Good job actually doing it though! I changed my mind because i was lazy and didnt believe it would help me much anyway. I look forward to more results though!

 

Thanks Swoley2k. I actually just finished this mod last night so I haven't had too much time to test it. I just upped the memory clocks to 500 and they are still stable. I'll post back when I have more results.

 

Nice job. + Rep. Would try this if finals weren't looming about.

 

Great idea and nice mod! The question is, where did you manage to get a spare?

 

Asus estore.

http://estore.asus.com/shop/

 

Thanks for the compliments guys. I can't seem to get my card to overclock above 550 core. Do you guys suggest driver level overclocking or bios?

 

I don't see the spreader available as I've been to the estore on a frequent basis checking for the copper versions. The VGA thermal cooler looks to be the heatpipe heatsink and not the aluminum heatspreader that comes with the 8600 GT DDR2..