Essential Guide to Semiconductors, The

Sorting the Fast from the Merely Good

Once each chip is tested to see if it's functional, it'll often be tested again to see exactly how fast it is. Natural (although unwelcome) variations in manufacturing will make some chips work slightly faster than others. If the difference is significant (say, 20 percent faster) and if the numbers of these overachieving chips are also significant (about 20 percent or more) then it's probably worthwhile to sell them at a premium price. For highly profitable microprocessor chips for PCs and other computers, this extra financial gravy can be more than $100 per chip.

Other times, it's not worth the trouble to sort the chips by speed. If a good chip sells for only $1.25, a fast one is unlikely to command a premium ...