CPU Lapping

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Lucrin

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Nov 30, 2009
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Ok so I recently got an i7 920 and I am very happy with it but I want to see how much overclocking I can do with it. When I got it I noticed there was a slight convex curvature to the IHS on the chip. I wasn't worried at the time cause I just wanted to make sure everything ran but now that I am looking into overclocking I wana make sure I am getting the best cooling I can. I looked at some guides and tips on lapping and I was wondering what grits I should use. Currently I plan to use 400, 600, 1000, 1200, 1500. I would like to use 2000 but my dad didn't have it at his store so I would have to go somewhere else to get it. Do you think not having 2000 grit will be a problem? Will 1500 make it smooth enough? Thanks.
 
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I advise against it. The possibility of a lower temperature is very remote. The difference will be virtually nothing. And if you mess up, you are screwed. Well, not really, but it could increase the temperature by like up to 5C.

It will be a waste of time.
 
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I lapped mine and it made quite a difference, however I believe my CPU was originally over-convexed. I realise now I should have simply exchanged the CPU (my temps were into the 80s so you know something was wrong) but I decided to lap it. I did a good job of it and temps dropped down to below 60C at the same clock. The thing is, it will void all warranties you might have for one. Secondly it can potentially damage the CPU if you do it wrong or maybe send a static spart through the pads on the bottom or you might just get finger oil on them and it won't have proper contact when you reinstall it.

If you're looking to do it tho, it will help at least a little and maybe a lot if your temps are high.

Your question about grits, well you're going overboard. Use 600 or 800 to get it to the flatness you're looking for (takes a couple hours) then at that point use 1000 grit for about 20 mins then 1500 for another 20 mins. You don't need it perfectly reflective, the point of thermal paste is to compensate for any scratches, but you have to make sure you get it flat. In reality even just 1000 grit is enough but a slightly better surface finish is nice to have. I used 800, 1000, 2000 and although it voided my warranty, the tech guys at the store were impressed with the lapping (burned out motherboard lol)
 
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Like other people have said, It's just not a good idea.

It voids the warranty (although if you're planning on overclocking, i guess that wont matter either as that would also void the warranty. if i remember correctly that is.) and if done incorrectly, can make your cpu worst than what it was.
 
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The warranty thing isn't an issue for me. I have done lots of other mod related things to hardware that void warranties and I haven't had a problem. As long as you go slow and make sure you evenly lap (by rotating) there is no reason you should have any problems. Anyway I already started lapping so too late to go back 😛 And so far I am glad I did. I am not completely through all the nickel platting yet but where I am through has revealed that the IHS surface actually had a C-shaped convex area around 3 of the 4 edges and the low area that wouldn't have good contact runs straight across 3 of the cores xD lol. Anyway thanks for the tips so far so good about an hour and a half in.
 
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I do this all the time since I rarely ever sell anything used, and work in a machine shop. Just make sure you're careful when you do it, that's all.

If 1500 grit is all you can get, don't worry about it. Diminishing returns. The point isn't so much the beautiful mirror finish, as it's getting that heat spreader as flat as reasonably possible.

Remember, let the sand paper do the work, don't force anything! Also, good practice would be to alternate direction with each grit.

If you're going to lap your processor, you may as well lap your cooler as well. Be careful on anything that has heat pipes that make contact with the CPU. These are hollow and you might rupture them.

Also, this might sound silly but it's pretty important. Consider how your heatsink is mounted. The whole process of sanding removes material. It's pointless to do this if you're going to have a loosely fitting heatsink, and might even make everything worse. You laugh now, but I've seen people end up with gaps and then fry their CPU/GPU/RAM/etc in seconds.

Lastly, if you get everything flat and shiny, apply even less thermal paste than normal. Assuming you still have a nice tight fit with your heatsink, you'll find a lot of thermal paste will get pressed out the sides. I use a razor blade to spread a very thin layer.

Good luck!

EDIT: About that C-shape you're seeing... You're probably right that the heat spreader was not flat. This is going to sound stupid... Just make sure that when you're lapping that you are not unintentionally favoring one side. Thing is, visualize this... Imagine if you had some divine block in your hand that was perfectly flat. Then you were told to remove 1mm of the bottom surface using a flat piece of sand paper. Because of human error, you will probably end up with a convex surface since you can't hold that block perfectly flat against the sand paper and will end up removing more material from the edges. I dunno, just a thought. :)

The sand paper you're using, you do have that mounted to a flat surface right, like a sheet of glass?
 
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Yes I used a sheet of glass as my flat surface and I rotated the chip consistently so any favor to one side I might apply would get balanced when it was rotated the other way. My razor blade test shows it is ultra flat and it actually suctions to the glass face a little. I am pleased it looks great and it runs about 4-5 degrees cooler which is a nice difference. Took me somewhere from 2-3 hours to do. Here is a picture of the finished chip (ignore the poor quality, just took it with my phone 😛)

0527002032.jpg
 
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Yeah It may look good but its gonna be covered in thermal paste and a heatsink on the top of it so who cares you cant see it anyways. I really dont know what the fascination of lapping is. 3 hours of work for 3to5 degrees of temp seems like a waste of time and if your chip fails somewhere down the road a waste of money. But if your made of money I guess the warranty void is nothing to you.

I hope you dont slap a garbage heatsink on it if so you would have wasted more time than you already have.

People in the cpu world always want to do things just to say they did them. IMO this is one huge thing people do just to say they did it.
 
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Its not really a waste since if you are overclocking you are voiding the warranty anyway and by lapping the CPU lowers the temp makes it better for your CPU lower the temps the longer the CPU will last especially when overclocking.

You just dont understand how us enthusiast are with our rigs. My computer is like family to me lol no well not like that but, I do put alot of time into it and something like lapping a CPU, adding fans, securing wires all are things we do to make our rigs the best we can get them. It is something to be proud of when its all set and done.

Lets put it like this you get a nice new car but well you want to make it a little special so you buy some new rims, install a nice exhaust system and put a big intake on it all stuff that will void a warranty but thousands of people do it. Then you polish buff wax and sit back and have pride in your work. Its the same with a computer its really just pride of ownership its not all that crazy.
 
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😱 It's so shiny.....

Sorry, just cant resist. :lol:
 
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Exactly! This is how it should be thought of. Anyway if you think about it 5 degrees sounds small but for an i7 920 5 degrees temp can be the difference between a stable 3.6GHz overclock vs. a 4.0GHz overclock. If you check out some benchmarks I think you will see it is worth striving for that extra performance. Also I am putting a ZALMAN CNPS9900A LED heatsink on it. Not considered the best but it is quite good. There are a number of people who report stable 4GHz overclocks with it on the d0 stepping chip (which I have so fingers crossed)
 
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All CPUs should be mirrored finished, and by the look of it you have done a fantastic job i'm just wondering how you managed not to get any metal & sandpaper particles all over your CPU, i think it would be harder doing the same to a cooler...
 
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I just got a badge for this thread getting over 10,000 views so I thought I would come back and let anyone who is considering lapping know that it can be done successfully. The core i7 920 pictured above was lapped and overclocked from stock 2.6GHz to 4GHz on air cooling four years ago and it is still running strong today. I have no doubt that lapping contributed to being able to maintain that overclock over the long haul and am really glad I did it.
 
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I have lapped dozens of cpu's and heatsinks. You can still get a mirror finish with 1500 as your max grit. Intel cpu's of today are pretty easy to lap because the heat spreader is small and they are ball grid array vs pin grid array.
 
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How would it increase the temperature by making the heat spreader perfectly flat? Lapping a cpu isn't risky if you are careful. Delidding is 1000X times riskier.
 
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This is a long dead thread.
 
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Skip the 400 grit. Its too course and will groove the heat spreader. You can get a good finish with 1500 grit.
 
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