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Old 06-09-2011, 07:16 AM
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TiN TiN is offline
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Default Bad OC? Maybe your CPU is bent. Fix here.

We were benching some LGA1366 CPU's, and found that eventually CPU did not clock stable anymore.

After some inspection and brainforcing problem was founded.

CPU IHS was not flat, and had bad contact to cooler surface.

Well known fix to that - lapping with sandpaper. So this thread dedicated to actual lapping and issues related to it.

When you just start to sand bent CPU truth became visible by naked eye.

You can see how bent IHS on this CPU. Wavy as old road.

Next step - sand top of IHS keeping surface as flat as possible, try to put equal pressure on all sides as close to 90 to sandpaper as possible. It's quite heavy task to do, so we make CPU holder from 1366 motherboard.

Also don't forget to apply water, as water help you to remove copper particles and make proccess easier.

As end result you should have flat surface on CPU IHS, to have good contact and good area for heat removal by your F1EE or F1 Gemini

No need to make mirror finish on IHS, it will not help, just waste of time. Enough to have finish by grid 400 or 600 sandpaper.

If you think this is not extreme enough, you may consider taking IHS off completely, but this is much more demanding process, and CPU is quite tricky to use.

Want to know more? Follow thread

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Old 06-09-2011, 09:47 AM
Cyph3r_Smurf Cyph3r_Smurf is offline
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Nice pictures Long time since i have lapped a CPU (Back in the celly days)
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Old 06-09-2011, 07:52 PM
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poparamiro poparamiro is offline
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Nice thread.

Ihs base with flat lapping and heatsink/pot base with convex lapping give best heat transfer. Convexity grade can be adjusted by the thickness of the glass. For that type of die (bloomfield/gulftown) must set higher grade of convexity.
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Old 06-10-2011, 10:05 AM
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Hyperhorn Hyperhorn is offline
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When you say "did not clock stable anymore" you mean CPU worked fine in the past under the same conditions, but then it changed (because the IHS contact became worse)? So when extreme low temperatures (LN2 in your case obviously) meet a certain mounting pressure it can deform the IHS of a CPU?
The Initial value finished
PI calculation is done!

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Old 06-10-2011, 06:09 PM
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G H Z G H Z is offline
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That's a damn nice lapping jig you have there
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