The size of the final die is very important to your yield from a single wafer. Imagine you have a 4in by 4in square. If your chips are 1in^2 you can fit sixtee

The size of the final die is very important to your yield from a single wafer. Imagine you have a 4in by 4in square. If your chips are 1in^2 you can fit sixteen chips but if your chip is 4in^2, you can only fit four. Now imagine you have a thick scratch going diagonally right down the middle. With the bigger chips, you might lose all four to that single error, wiping out your yield. With the smaller chips however, you'll only lose part of your wafer. Specialized processors like those made for mainframes or RAD hardened ones can be much bigger since the set up costs will vastly outnumber the fabrication cost anyway. Companies like IBM that aren't in as cost competitive a market as Intel make big chips all of the time.