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How Much Thermal Compound After Lapping Core i7 930 and Cogage True Spirit?

post #1 of 5
Thread Starter 
So, I took the plunge this past weekend and lapped both my Core i7 930 and my Cogage True Spirit.

You can still see lots of scratches left from the 220 grit I started with, but from angles, these look deceptively mirror-like.




Unfortunately, this has yielded me pretty much 0 improvement. I'm running two Akasa fans rated for up to 83 CFM in push-pull. The cores are a little more equal at load, but I'm still hitting a max of around 72 C on Core 0 (measured by Realtemp) with an overclock to 3.8 with Prime 95 torture test (Ambient temp around 24 C. Vcore is set to normal. CPU-Z shows 1.2, BIOS shows 1.2125. I don't think it helps that I think I got a crap 930, but that's besides the point.

As for the lapping, it's by no means perfect, but there's a large improvement in flatness. I checked with a precision flat edge and it's definitely not perfect. The edges don't have the greatest contact, (I can shine a light and see it around the edges) but it's flat in the middle where it counts and it's miles better than it was to start with. The heatsink feels much more stable when installed. Before, if you put a little too much pressure while installing the fans, you could feel it turn, but that's not the case anymore.

Anyway, I have a theory that maybe I'm using too much Arctic Silver 5. I pretty much had a perfect bead, just as shown on arctic silver's website. Am I using too much now since I've got a much flatter, more polished surface? Is Arctic Silver taking into account a higher level of uneveness and roughness when they make their recommendations? Should I go with much less compound as there's less uneveness to make up for now?

Anyway, your thoughts are appreciated. I'm sure I'll reseat this thing in the not too distant future, but I'd like opinions.
Edited by breenemeister - 1/31/11 at 7:37pm
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post #2 of 5
You would use just as much as you normally would even after lapping.

If you are running at stock, you probably won't see too much of a difference. I bet if you ran at 4.0, you would have been able to see a difference between before and after.
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post #3 of 5


I Agree, you still have the same area even after lapping. Use the same amount as you would.
post #4 of 5
lmao, lapping on the CPU comes out as "rubbed"
Edited by SpeedNuggeT - 1/31/11 at 9:17pm
post #5 of 5
Thread Starter 
Quote:
If you are running at stock, you probably won't see too much of a difference. I bet if you ran at 4.0, you would have been able to see a difference between before and after.
I'm running it at 3.8 GHz with a similar ambient temperature and got pretty much identical results before and after. Of course, I did switch from Shin-Etsu to AS5 in the process and it's not yet broken in. However, I really doubt there's that much difference between the two compounds.

Quote:
lmao, lapping on the CPU comes out as "rubbed"
Nice observation, I didn't even notice that!

Quote:
I Agree, you still have the same area even after lapping. Use the same amount as you would.
Thanks for the responses. Let me propose this though; before and after lapping, you have roughly the same surface area to cover, for the most part. However, if you take into consideration that the heatsink and CPU heatspreader both had a pre-lapped texture to them with lots of nooks and crannies to fill up as well as convex and concave curves to bridge between the parts, there should actually be slightly less surface area and a shorter distance to bridge between concave and convex parts after lapping. The ideal thermal transfer would occur between two perfectly flat, non-porous surfaces mated together with no thermal compound. By that token, wouldn't it make sense to use at least slightly less compound if you have two very flat, smooth surfaces since the compound has fewer places to "hide" between the heatsink and CPU heatspreader? In theory, too much compound would act as an insulator and actually become a barrier between two perfectly flat pieces of metal.

All that said, in this area, you guys have a lot more experience than I and most of the time actual observation and experience wins out over theory as we seldom achieve perfect results with something like lapping. I just wanted to propose more theory to see what you thought.
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Black Sunshine II
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