For those who still do not get the benefit from lapping two surfaces, let think of this in a different larger way. If you take a fork, the kind you eat with, and deeply scratch a flat surface of wood with each point of the fork, say 4 points on this fork. Now that you have 4 scratches, observe their depth. Question 1: Does this increase surface area? Yes! Question 2: Does this increase surface contact? No, it reduces surface contact. Take a small piece of glass and lay it on top of the wood, this will simulate your CPU surface. Do you now see that those scratches will not contact your glass, CPU. Next, what is in those scratches, air. Air heats up very quickly and does not transfer heat well at all. Infact, air pockets will create hotspots, so where these scratches are will infact remain cooler on the heatsink and hotter on the CPU since they don't make contact. Next, heatsink compound, it will fill in these scratches or gaps, but its main purpose it to eliminate air pockets and small imperfections between the surfaces and reduce the hotspots between the contacts. So back to you model with wood and glass. Fill the scratches in the wood, slightly overfill them so you have a rise is the oil above the surface, with a light cooking oil or water and replace the glass. You should now observ the oil flatten out across the entire surface between the scratches, if you didn't you did not use enough oil or water. Now if you apply light pressure to the glass with you finger tips spread open across the glass you should notice even more speading of the oil, possibly squeeze out beyound the glass or wood. This is because all of the oil has filled the holes and now has to escape. This actual surface contact has not really increased, you still have the scratches in the wood, but the oil will transfer some of the heat to the glass now, having reduced air pockets. Apply this knowledge to CPU's and heatsinks. This concludes lesson 101. Still don't get it? Put a frying pan on a burner, put the heat on low, and rest your hand on the pans flat surface for a few seconds, probably hot, but what happens when you press down with your hand, it flattens out more, reducing air pockets, increasing heat transfer, making your hand even hotter. Now put cooking oil in the pan, this will fill in any grooves, finger prints, etc... on your hand, and press down hard, probably even hotter than without the oil. Get it yet? If not you have no reason to be touching a computer, go back to picking up garbage on the highway or robbing people and smoking crack because you are a lost soul.
