In the summer of 1981 I was asked to consider the possibility of manufacturing a 600,000 transistor microprocessor in 1985. It was clear that the technology would only be capable of manufacturing 100,000-200,000 transistor chips with acceptable yields. The control store ROM occupied approximately half of the chip area, so I considered adding spare rows and columns to increase ROM yield. Laser-programmed polysilicon fuses would be used to switch between good and bad circuits. Since only half the chip area would have redundancy, I was concerned that the increase in yield would not outweigh the...