Soldato
How many CPUs did they have to go through in order to get these hand-picked 20? 100? 10000?
They would have a good idea from where the silicon is in wafer, and how new the mask was.
After that the CPU's are automaticly tested after they are packaged.
the process is far more simple then one man physicaly testing from just random batches, although it is possible they speed bin the 'cherries' post production too.