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  1. #1
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    Lapping the cpu die

    Anyone here done this or is there a guide for it? Just curious if its worth it.

  2. #2
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    Oh geeze. I suppose I'm curious to see what sort of replies this gets... I've still never heard from anyone who's actually done it... but I can't imagine it's worth the risk.

    Let's see.
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  3. #3
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    Wouldn't this kill the cpu?

  4. #4
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    Originally posted by TLMiller
    Wouldn't this kill the cpu?
    That's the trick, ain't it? The theory is that you could probably polish away a considerable amount of the die surface without damaging the chip. These things are so sensitive, though, and generally precious enough.... you won't catch me doing it any time soon.
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  5. #5
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    i would try it for an intel, not amd atm, heh.
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  6. #6
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    Chips that had a metal plate on top of the silicon core sometimes had dips in the plate. These you could lap fairly safely, but there were still risks in doing it. The plates were not very thick and you ran the risk of cutting through the plate.


    If you were not very careful, small almost microscopic metal particles could get caught around the pin area and increase the chance of shorting out the cpu or the socket on the motherboard.


    Lapping the CPU went out of practice with the newer chips that did not have the metal plate, as the circuits are not far under the surface of the top layer. The potential of destroying a new cpu is extremely high and the benefits of directly lapping silicon are not that great, as the wafers are usually pretty flat from the manufacturing process.

    I personally would not lap a new chip.

    I did lap a K6-2 300 once that got very hot and I did not have a problem, but I knew someone that killed his K6 trying to lap it.
    It is said that whosoever the gods wish to destroy, they first make mad. In fact, whosoever the gods wish to destroy, they first hand the equivalent of a stick with a fizzing fuse and Acme Dynamite Company written on the side. It's more interesting, and doesn't take so long.

  7. #7
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    Originally posted by Brooks
    I did lap a K6-2 300 once that got very hot and I did not have a problem, but I knew someone that killed his K6 trying to lap it.
    Interesting... hey, maybe in response to perdomot's original question (and to satisfy my curiosity), could you give us a rundown on what that procedure was? I mean, physically, mechanically -- what does this project look like?
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  8. #8
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    I did it just like one would lap a heatsink now, with a couple of minor alterations.

    I was afraid of metal getting into the pin area from the metal cap on the CPU, so I took a piece of foam rubber and put the cpu pin side on it. Then I took tape and taped the edges of the foam rubber to the edge of the die.

    I then just started out with some 400 grit and finished with 800 grit sandpaper.

    I tried to only grip the CPU along the edge and never in the middle to try and prevent damage to the pins and not to crack the core. I used a very light grip and never grabbed it hard. I also wound up sanding my fingertips because sometimes my hand would slip off due to my light grip.

    It took longer than a heatsink does because you can't apply as much pressure in the lower grits to remove the metal faster.

    I also checked the cap often to try and determine if I was getting too close to damaging the chip.

    After finishing, I used some air to blow off the top and then took off the tape and foam rubber and gave it a second blowing.

    It was much smoother and the little dip was gone. It did seem to help as the system was stabler and the heatsink got hotter than it did before.

    I was going to have to replace the chip anyway as it would get so hot that you needed gloves to touch it and those AMD K6 chips were easy to burn up. It would crash in less than an hour and you had to wait a while to use it again.

    So I really had nothing to lose. I got longer life out of it and saved myself most of a weeks salary. (I was on a much more limited budget back then)


    As I said earlier, I would not want to try and lap a cpu where the silicon is directly exposed. I would be so afraid of killing the processor.

    The metal cap was a whole different beast and I was needing a cheapish fix. $10.00 or so dollars of sandpaper, a mirror and some scraps of foam rubber was a whole lot cheaper than a $150.00 cpu when I was only working part-time and going back to college.
    Last edited by Brooks; 09-12-2003 at 03:26 PM.
    It is said that whosoever the gods wish to destroy, they first make mad. In fact, whosoever the gods wish to destroy, they first hand the equivalent of a stick with a fizzing fuse and Acme Dynamite Company written on the side. It's more interesting, and doesn't take so long.

  9. #9
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    i was looking for some old guides for lapping old style chips (metal heatspreader) and found one for flip chips

    you wont see me doing this to my barton

    http://www.froggy.com.au/frogge/pepp...apreport1.html

    if you look at an AMD chip close up they are grainy but as someone said earlier very flat I dont see much room for improvement


    maybe some fool.....er., i mean “user” here could try this out on an old chip and see what happens


    *EDIT* another time I should read then post, aparently the pIII's have a blue plastic coating on the core and lapping them nets improvements, AKIK there is no sealer on top of an athlon only the sides
    Last edited by RavenTai; 09-12-2003 at 03:29 PM.

  10. #10
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    Interesting link, RavenTai. Makes me wonder if one can grind down a die (or a heatsink, for that matter) deep enough to compromise the intended clamping force of the heatsink's clips or bolts. Probably not; you probably can't go far enough into the die, at least, to achieve that effect without biting into the CPU's guts.
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  11. #11
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    Originally posted by mlocher
    Interesting link, RavenTai. Makes me wonder if one can grind down a die (or a heatsink, for that matter) deep enough to compromise the intended clamping force of the heatsink's clips


    maybe not to interesting I jumped the gun a bit. I did not read the intro just skimed to the results (and was shocked to see such in increase) when I posted that link, see the edit above AFIK dotn think that applies to Athlons

    I am pretty sure you cannot reduce the clips leverage from CPU lapping without killing the chip, heat sink lapping it is a possibility but you would have to really go overboard to remove enough metal to reduce clamping force

    with the Hammers (and their metal heat spreaders) about to move into the enthusiast market CPU lapping may soon be an issue again
    Last edited by RavenTai; 09-12-2003 at 03:43 PM.

  12. #12
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    Intels P4's really need laping, intel says the metal expands when it gets hot, but they are lieing. I had a dead 2Ghz and the thermal pad had only made contact on the edges.
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  13. #13
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    Interesting replies. The reason I posted the question was that I was cleaning off my old 1600+ Palomino and noticed the writing on the die. I suppose the AS3 fills these in but how much of an effect do you think it would have if you lapped it with 2000 grit just so that the entire die was complete flat. In other words, go down only as far as the depth of the writing.

  14. #14
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    Originally posted by perdomot
    I suppose the AS3 fills these in but how much of an effect do you think it would have if you lapped it with 2000 grit just so that the entire die was complete flat. In other words, go down only as far as the depth of the writing.

    hmm I forgot about the lettering on older CPU's, yes as3 woudl fill that void but it is best to get core to heatsink contact when you can, I would assume diffrence would not be much but that is just a guess, if you do this please get good before and after tmeps in the same case, same motherboard, same HSF assy, room temp etc.

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