|Lapping the core / slug flat :|
Check your core's / slug's flatness against the light :
Using the backside of a caliper :
Fasten the emery paper using cello' tape to the glassplate and make sure it's no bulges - you shall always use water on the emery paper when gritting :
Hold the tongue straight in your mouth and the slug 100% aligned /leveled with the emery paper when you are gritting... Check the slug often to see if the flatness improves - with a caliper as mentioned above.. If you haven't done this before or are insecure - get a mechanic to help you !
Flush the emerypaper under the water tap often to ensure it is as clean as possible at all times. Don't dry off excessive water - just shake it off ...
I always start with a grade 1000 paper and then use a grade 2000 paper when the slug is nearly 100% flat. When it's flat I polish it with a grade 6000 paper.
Look at this mirror ! , and I only used one hour to achieve this ....
Before lapping/gritting/polishing the slug I could run this PIII450 - SL37C stable at 133MHz FSB (600MHz) on AbitBX6r2 -- I could also run it at 138MHz (621) FSB - but experienced random reboots...After lapping it in I never experienced a reebot anymore.. I could never run it on higher FSB's on AbitBX6r2.. So I moved the CPU over to AsusP3BF - and it were 100% stable at 140MHz FSB (630MHz)...with a Alpha PIII cooler.
The professional lapping technique !
This is the best way off lapping your CPU. Using a lappingplate and polishingpastes ensures that you will get a 100% flat CPU. A lappingplate is expensive though.
You should NOT move your CPU in circles or back and forth when you are lapping : a " 8" motion is correct - ( but it's not always possible with some PII and PIII's). The goal is to make the whole slug 100% flat and with the smoothest possible surface. A smooth/ flat surface = better heattransfer as less grooves/stripes will allow you too use less heat - transfer compound.