Is your Northwood this flat?

[Binge]

I wasn't going to bother with it - but I figured wtf.
So I set out to lap my 1.6a Northwood today before its installation.
Whoa - the chip was major convex as you can see from the picture.
I would definetly recommend lapping your Northwood.

Check it: Northwood initial Lapping

I continued with higher grit paper and got it to a nice mirror like finish.

 

[mschell]

I don't think lapping the Intel chip will get you much considering the surface area provided by the heat spreader. The heat spreader was designed to reduce thermal interface variables with the HSF unit. This means much less care is needed when attaching the unit and the selection and application of thermal paste is not so critical as well. Another point to consider - common wisdom says the layer of thermal compound between the CPU and HSF should be as thin as possible. Lapping accomplishes this by lowering the high spots but is possible to have too little clearance between the materials, the tight clearance actually hangs up on the grains that make up thermal compound chief heat transfer medium, silver oxide for Artic Silver, aluminum oxide for RS paste. Another problem is the small clearance doesn?t allow for much carrier (the stuff that makes the paste liquid). The carrier in any thermal paste will oxidize or evaporate over a period of time, less carrier equals faster evaporation equals loss of thermal interface.
The key to the thermal interface layer (thermal paste) is not too thick, not too thin, somewhere in between - just right.

Get the technical docs from the makers of the particular thermal paste you are using. They should list the optimum thickness for the medium.