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Lapping CPU?

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  • CPUs
  • Tuniq
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May 8, 2007 3:42:20 AM

HI all, I wanted to know if its a good idea to lap a CPU before using it? What if its a DOA? I have lapped my Tuniq Tower 120 (can see my face in it) and I know that my CPU is Not flat, its high around the four corners/concaved. Am I overreacting or should I just do it? Thanks

More about : lapping cpu

May 8, 2007 4:03:37 AM

Quote:
wanted to know if its a good idea to lap a CPU before using it? What if its a DOA?

They rarely are, but you can build a system, make sure everything is working right and then lap.
May 8, 2007 4:12:27 AM

help a brotha out... what the hell is lapping?
May 8, 2007 4:17:40 AM

Quote:
help a brotha out... what the hell is lapping?

Quote:
Polishing to a high sheen and flat surface, start out with large grit and work your way down, then finish up with polishing paste.


at the end it looks like this
May 8, 2007 4:17:52 AM

Seems like a lot to risk for a cooler temp.
May 8, 2007 4:18:50 AM

no risk, just voiding the warranty
May 8, 2007 4:25:45 AM

I guess I wouldn't risk it to void the warranty. Especially if the cpu was one of the newer, $400+ cpu. Thanks for the lesson on lapping
May 8, 2007 4:37:05 AM

Why don't amd and intel just make the heatspreaders flat to begin with? It can't be that much more expensive to do that. I guess it just takes too mcuh time for them.....
May 8, 2007 4:39:25 AM

To lap my HSF I used a thick piece of tempered glass then put some 800 grit with some water under the sandpaper so it won't move around. How thick is the heatspreader on the CPU? I am considering doing it...
May 8, 2007 5:13:19 AM

There would be difficulty in placing required information on the CPU if the chips came prelaped. All the identifiers would have to go on the underside. Quite a feat for AMD to accomplish, and for Intel chips, they'd have to be mighty creative to do it.
May 8, 2007 5:21:41 AM

I lapped my notebook's P4 and temperature drop by few degrees only. Unless your CPU heatspreader is not leveled there shouldn't be a need to do it. But it takes time for a good lapping
May 8, 2007 5:46:21 AM

OMFG! LGA 775 I was pushing very softly to get me CPU into the socket and bent two pins! How do I bend them back? I thought I was to apply some pressure for it to go in? What do i do now?
May 8, 2007 5:49:14 AM

try to bent them back with a needle or something small, be carefull though
May 8, 2007 5:50:01 AM

Your local plate glass replacement shop should be able to help out here, cheaply if you don't care about artery-slicing edges....

I like the water based grits, available at most good carpentry shops in grits from 800 to 5000.

Your piece of plate will need to be replaced often if you do this a lot, so become friends with your local glass shop. The grit can be dried and re-used several times with no ill effect. (that's why I like the water-based)

If using a cpu with pins, it is probably a good idea to use some conductive foam on the pin side of the CPU. Even with BGA chips its a good idea but will require some carefully applied tape to hold it in place better. I've heard of using aluminum foil, but I'm of the old school 'better safe than sorry'.

My 2p
May 8, 2007 5:59:49 AM

Does the CPU just rest onto the pins or does the CPU need to be push through the pins a little? Is there some place i can take my mobo to get them fix by someone that knows how to get the pins back?
May 8, 2007 6:02:34 AM

you you're suppose to to gently put cpu on to the mobo socket, no force needed. i guess you can try to call any local pc store, compusa, bestbuy etc.
May 8, 2007 6:15:35 AM

Did you break them or bend them? If they are broken you are probably screwed. I'm sure even that COULD be fixed, but good luck with it. If you are REALLY lucky they may not be used, so I would plug it in and try it out, some of the pins aren't used for anything, it might still work... If they are bent then I would try, very carefully, to straighten them out with a needle.
May 8, 2007 6:17:27 AM

he said he bent two pins, not break
May 8, 2007 6:28:30 AM

I was able to bend the pins back, but they aren't angled the same as the others so when i clamp it down with the lever are they going to bend down at the angle olike the others?
May 8, 2007 8:04:36 AM

It's hard to know without photos. Try it and find out.
May 8, 2007 8:51:22 AM

I got the two pins bent to the right angle now, but one pin is just a little (I mean very little) shorter than the rest. Is it ok to have one pin a hair shorter than the rest?
May 8, 2007 11:07:01 AM

Quote:
I guess I wouldn't risk it to void the warranty. Especially if the cpu was one of the newer, $400+ cpu. Thanks for the lesson on lapping

Question, do you plan to overclock? Because that automatically voids the warranty. So if you plan to do such, might as well invest the time into lapping and please, I mean please, do not use Arctic Silver 5 on a lapped IHS.
May 8, 2007 11:53:41 AM

o_O why not? What's wrong with using AS5?

:idea:
May 8, 2007 12:08:34 PM

Nothing is wrong with Arctic Silver per say, but think about it logically. AS5 is used to bridge the gap between the IHS and the heatsink base by filling in the microscopic ridges and grooves on the IHS and HSF. Lapping, when done at least partially correct smooths the surface of both the IHS and HSF, providing more surface area for heat to be dissipated from and removing the microscopic grooves which AS5 fills in.

Now when you lack those grooves and ridges on the surface AS5 only acts as a barrier, preventing proper heat flow and can in the end, cause higher than projected temperatures. That's why you don't use a silver or (most) metal based thermal goops when lapping and use silicon based goops which fill the area better than AS5 and the like.

There is a point when the lapping is done so well that you don't even use a TIM but none of us will ever reach that point.

AS5 is good for a stock surface. Other than that, it's being wasted.
May 8, 2007 12:29:02 PM

Quote:
I got the two pins bent to the right angle now, but one pin is just a little (I mean very little) shorter than the rest. Is it ok to have one pin a hair shorter than the rest?


It could just be a grounding pin. Give it a shot.
May 8, 2007 12:34:10 PM

Theoretically I'd say you are right Ninja but good luck getting there. Personally I think that lapping the heatsink surface to a mirror finish may be counterproductive. Ninja hit it on the head when he said it will get to the point that the TP acts more like an insulator than a conductor.

Lapping the HS to a flat surface is an excellent idea (although Swiftech found some benfitto a slightly conves surface along the core axis) but having a slightly rough face to it is better for heat dissipation than a completely flat, mirror-smooth finish as it leaves room for the TP to expand and contract, for heat to move around and channel itself and the two surfaces to properly mate. Several heatsink manufacturers specifically recommend that you do NOT lap to a mirror finish

Lastly, lapping your CPU makes it all but worthless for selling on the open market. It is fine if you are in tight with a bunch of overclockers but forget selling it to anyone outside your circle of friends.
May 8, 2007 2:57:22 PM

Quote:
Nothing is wrong with Arctic Silver per say, but think about it logically. AS5 is used to bridge the gap between the IHS and the heatsink base by filling in the microscopic ridges and grooves on the IHS and HSF. Lapping, when done at least partially correct smooths the surface of both the IHS and HSF, providing more surface area for heat to be dissipated from and removing the microscopic grooves which AS5 fills in.

Now when you lack those grooves and ridges on the surface AS5 only acts as a barrier, preventing proper heat flow and can in the end, cause higher than projected temperatures. That's why you don't use a silver or (most) metal based thermal goops when lapping and use silicon based goops which fill the area better than AS5 and the like.

There is a point when the lapping is done so well that you don't even use a TIM but none of us will ever reach that point.

AS5 is good for a stock surface. Other than that, it's being wasted.


So what would you use instead of the AS5 Ninja? Arctic Céramique or Arctic Alumina?
May 8, 2007 3:23:23 PM

Quote:
Theoretically I'd say you are right Ninja but good luck getting there. Personally I think that lapping the heatsink surface to a mirror finish may be counterproductive. Ninja hit it on the head when he said it will get to the point that the TP acts more like an insulator than a conductor.

Lapping the HS to a flat surface is an excellent idea (although Swiftech found some benfitto a slightly conves surface along the core axis) but having a slightly rough face to it is better for heat dissipation than a completely flat, mirror-smooth finish as it leaves room for the TP to expand and contract, for heat to move around and channel itself and the two surfaces to properly mate. Several heatsink manufacturers specifically recommend that you do NOT lap to a mirror finish

Lastly, lapping your CPU makes it all but worthless for selling on the open market. It is fine if you are in tight with a bunch of overclockers but forget selling it to anyone outside your circle of friends.


This is a big point. In many cases, a certain amount of roughness is actually preferred. It creates more actual surface area, which allows for greater thermal exchange. Ideally, there would be perfectly interlocking nano-ridges on the IHS and heatsink.
a b à CPUs
May 8, 2007 3:56:33 PM

Why do you need a mirror finish? are you going to do your makup in it? I lapped mine untill it was flat and basically smooth. I used 400,800,1000,1200 paper or was it 200,400,800,1000. I cant remember it was a 4 pack at autozone. I lapped it with the roughest untill all the coating was removed to the bare copper then worked my way up. Both surfaces were very smooth but not mirror finish. The TIM will fill in any imperfections and there is no way to get it pefectly flat and smooth even with polishing and all that. I believe the goal of lapping is to make both surfaces relatively flat so that they can transfer heat better. The TIM just fills in the gaps and creates a compelete seal. My lapping gave me 5C on load and about 1C-0C on idle.
May 8, 2007 7:41:35 PM

AS Céramique or Shin-Etsu X23.
May 8, 2007 11:26:32 PM

Quote:
AS Céramique or Shin-Etsu X23.


Yeah I read your TIM post good read. I was debating on lapping my Tuniq and E6600. But now I'll wait till I can order some Shin-Etsu. Thanks Ninja
May 9, 2007 1:34:20 AM

At the very least lap your HSF as the surface on my Tuniq Tower 120 was rough and when I started wet sanding with 800 grit it was high in the center. When I was done it was perfectly flat and most CPU's are flatter than most HSF as was my case, but thats where Tim comes in. O yeah I was able to replace my mobo, what a si of releaf. :D 
May 9, 2007 1:53:57 AM

Quote:
Theoretically I'd say you are right Ninja but good luck getting there. Personally I think that lapping the heatsink surface to a mirror finish may be counterproductive. Ninja hit it on the head when he said it will get to the point that the TP acts more like an insulator than a conductor.

Lapping the HS to a flat surface is an excellent idea (although Swiftech found some benfitto a slightly conves surface along the core axis) but having a slightly rough face to it is better for heat dissipation than a completely flat, mirror-smooth finish as it leaves room for the TP to expand and contract, for heat to move around and channel itself and the two surfaces to properly mate. Several heatsink manufacturers specifically recommend that you do NOT lap to a mirror finish

Lastly, lapping your CPU makes it all but worthless for selling on the open market. It is fine if you are in tight with a bunch of overclockers but forget selling it to anyone outside your circle of friends.


Excellent points mate.
May 9, 2007 2:23:22 AM

I thank you sir and the same to you. Looking as I do, a mirror finish isn't a good thing anyways.
May 9, 2007 3:44:27 AM

It is pretty though. Here is an old socket 478 Celeron 2.8Ghz that I lapped.


Sweet cell phone picture too.
Edit: It is basically a perfect mirror finish, cell is just a little dirty at the time I guess, and it take crappy pics anyway.

I lapped with 220/400/600 and that proved to be better temps than going all the way to 1200 and Mother's polishing grit.

It was overclocked around 3.8 and I think at 600 grit I gained 7C under load and at 1200 it was only 4C better than stock. I was just curious and didn't do more than one application so don't put too much stock into the results, but it should be fairly accurate.

Lapping = quest for flatness, not smoothness.
May 9, 2007 1:10:47 PM

I'm just worried about messing something up personally. I mean my temps right now are slightly above ambient at idle and around 44 to 45C at load at 3.5 OC on an E6600. I just can't bring myself to believe that if I lap that my temps will go down even more I personally think these temps are great but that's just my opinion I guess. When I get up the nerve I'll do it and see if they improve any. On a side note if I lap my E6600 what should I use to hold it? Won't water getting into it or dust hurt it? I'm a lapping newb so any help is greatly welcome.
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