I’m always impressed with the folks at visual6502.org. This time, they’ve opened up an early CMOS chip, the RCA 1802 micro. It’s kind of like a proto-LSI time capsule. This chip was developed in the mid-1970’s and had radiation resistance, so it made its way into a number of spacecraft, including the Galileo probe.
Not only was the C2L CMOS process simpler, denser and faster than previous ones, it lends itself to radiation-hard chips, which led to this CPU being found in various space probes. (The bulk silicon process used for our RCA 1802 is not as radiation tolerant as the later silicon-on-sapphire processes, but it was better than other contemporary processes.)
As it happens, it’s also a great process for us to photograph and analyse, because the N and P structures show as different colours, and the layout is very readable.
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