We now routinely buy personal computers in which microprocessors with millions of transistors perform at gigahertz speeds, so it is easy to forget that the first microprocessor was not a simple or obvious choice to produce. At the time it was being contemplated, metal oxide semiconductor (MOS) technology was still quite new, and integrated circuits themselves had existed less than a decade. While MOS circuits with a thousand transistors were being manufactured, the economics of integrated circuits of that day limited how far the technology could be pushed. A 2-in-diameter silicon wafer, costing perhaps US$50 to process, might have a 10% yield for a 0.02-in2 die. If we pushed the die size higher, there would be fewer potential die per wafer, and yield would fall precipitously. Table 1 shows how the die cost might vary with die size.
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