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Temps after applying AS5 Thermal Paste to 6870 Stock cooler

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November 18, 2010 10:37:01 PM

Hey forum,

I just took apart my Sapphire 6870 with the stock reference cooler to apply some new thermal paste. There was a crap load of thermal paste on the GPU before where it had spilled over on all 4 sides. I cleaned it all up along with the heat sink with some 70% alcohol wipes and a lint free cloth. Then I used the simple dot method on the GPU die with some Arctic Silver 5 Thermal Paste, then reinstalled the heat sink and cover.

With an over clock up to 900 MHz on the core and 1100 MHz on the memory, the stock temps were about 55 degrees Celsius at idle and 82 degrees Celsius under load after 20 minutes of FurMark 1.8. After changing the thermal paste, the new temps were only 48 degrees Celsius at idle and only 74 degrees Celsius under load after 20 minutes of FurMark 1.8

So to summarize, after putting some Arctic Silver 5 thermal paste on the reference cooler on the 6870 and with a 50 MHz over clock on the core and the memory, the temperatures dropped by 5-10 degrees Celsius.

Has anyone else tried changing the thermal paste, and if so, what temperature changes did you notice?
November 18, 2010 11:00:17 PM

I definitely recommend changing the thermal paste on the GPU. Like yours, mine was all gooey and excessively applied. It lowered my temps about 5c and the fan by about 5%. It was really easy to do too. I used Zalman STG1, which comes with a brush applicator, and applied it very lightly over the entire GPU surface.

Three things: I would go for a higher alcohol content (91%) to evaporate faster. Second, is a big caution when unscrewing the screws on the heatsink. Use the right size screwdriver and be careful. With mine, I stripped the screw socket (where the screwdriver head fits) a bit which made it harder to get the screw back in tightly. Finally, now a couple months later I am having a potential RMA issue with my Asus GTX480; which I'm assuming is unrelated to my replacing the thermal paste. The point is, the warranty fine print says "warranty void if card has been disassembled". I'm hoping they won't figure it out when I return the card, although the stripped screw socket is a dead giveaway.
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November 19, 2010 1:29:03 AM

See, I got lucky because I have this awesome double ended magnetic screw-driver where each end is removable and double sided with a flat and a Philips head of two different sizes that fit both screw sizes perfectly. As for the warranty but, the computer store I bought it offered a 2 year replacement plan for an extra $15 where it cn be replaced up to 3 times a year for the two years in store.

In regards to your Zalman STG1, I've never used thermal paste that's applied with a brush before, I've always stuck with Arctic silver 5, or the tube that comes with come Cooler Master Heatsinks.

I am happy to see that me results are on par with others.

I was thinking that once the after market coolers come out specifically designed to fit a 6870, I'll get one of those and put it on just to cur the noise level down. The blower fan on the stock 6870 cooler gets loud above 30% and can be heard above all my other fans when they're set to max speed.
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November 19, 2010 1:32:00 AM

Reapplying thermal compound on a new card can be a mixed bag. Sometimes to much is applied, sometimes it isn't even, but those cases are rare. I've replaced the TIM on several GPU's and never saw a single difference. I've tried AS5, AS Ceramique, and also MASS COOL Shin-Etsu. Never saw a single difference. This was on several different cards that I've owned in the past. I've replaced it on a card that was older and was all dried up, THAT made a difference. And once replaced it for someone that had a card where it wasn't applied over the entire gpu, that made a slight difference of maybe 2C.

Just throwing my 2 cents in here. I leave it alone unless it is over the standard temps.
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November 19, 2010 1:35:46 AM

Well my big thing was that the stock cooler gets loud when it's turned up to account for overclocking. So if you overclock you either have to increase the fan to being loud, or find another way to help cool it, so my solution was to replace the thermal compound. Not many other options
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November 19, 2010 3:08:28 AM

Well, after some crashing during games, I'm starting to become convinced that my card is cutting out due to high heat. I can hear the fan getting much louder than usual, then either BSOD or the PC just shuts down. Hopefully, it's not because I took the heatsink off to replace the TIM and then failed to make a good connection with the heatsink afterwards. If I weren't returning the card under warranty, I would try again with new TIM, like AS5 or the new Zalman STG2, and make sure the heatsink is correctly installed. I guess if the RMA doesn't take care of the problem, then I may be looking for an after-market cooler... or a new GTX580 like jay2tall has.
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November 19, 2010 3:21:07 AM

Well don;t forget that a BSOD and crashing could also be from your CPU overheating as well. Just something else to think about looking in to if you haven't. Hopefully the RMA does fix the problem though.
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November 19, 2010 4:38:35 PM

After doing a little reading, it looks like the method used to apply the thermal paste may make a difference. With my card, and I assume the 6870, the heatpipes are direct touch. This requires you to use a method that will fill the grooves between the heatpipes, which might prevent the past from squeezing out to the edges. Froom my reading, just putting a dab in the middle won't do that for a direct touch heatpipe. You need to put lines down the heatpipes, and fill in the grooves between.

For my method, I very lightly covered the entire GPU and put very, very little on the heatpipes. The brush applicator makes it easy to do. Any thoughts on this method? Should I have used more paste and focused more on the heatpipes, instead of the GPU surface?
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November 19, 2010 5:03:17 PM

Well I know with my Cooler Master 212+ CPU cooler, it had direct contact heat pipes and I needed to do two small lines to get a good contact. The heat sink on the stock 6870 cooler does have heat pipes, but it's actually a flat copper plate that names contact with the GPU, so the dot method worked perfectly fine. After I tightened down the heat sink, I took it back off just to make sure the paste spread evenly and it did, then when I putthe heat sink back on, I made sure to tighten down one side before the other so and air bubbles could escape.
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November 19, 2010 8:43:54 PM

I went out and got a tube of Arctic Cooling MX-3. Hopefully, I can report back that my issue was solved with reapplying some thicker paste using a different technique.
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November 19, 2010 8:54:42 PM

Nvidia gpu's are going to need more paste, especially Fermi's , they have a pretty large heat spreader on the actual gpu die, as opposed to AMD' cards. Its hard to express how much is enough. But I would not be conservative, and use a grain of rice amount.
Thats one term , I've seen expressed before. Probably a pea, a big pea :) 


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November 19, 2010 8:56:12 PM

notty22 said:
Nvidia gpu's are going to need more paste, especially Fermi's , they have a pretty large heat spreader on the actual gpu die, as opposed to AMD' cards. Its hard to express how much is enough. But I would not be conservative, and use a grain of rice amount.
Thats one term , I've seen expressed before. Probably a pea, a big pea :) 
http://tpucdn.com/reviews/Powercolor/HD_6850_PCS_Plus/images/front_small.jpg
http://tpucdn.com/reviews/Point_Of_View/GeForce_GTX_460_TGT_Beast/images/front_small.jpg

I generally put on just enough to cover the logo mostly up, but thats just my thing.
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November 19, 2010 11:25:29 PM

In reading about the paste I used, the Zalman STG1, they said it was watery, maybe too watery. I put a REAL thin film of it on the GPU, which just barely covered the lettering. I think with the direct touch heatpipe, it maybe wasn't enough. It worked great for about 4-6 weeks though, but I now recall seeing the temps gradually creep up. I think the MX-3 I got might be one of the best on the market, so we'll see if a new application helps.
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