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This is fascinating. Really enjoyed reading this as a lay-person. The only bit I struggled to follow was matching up the diagrams with the actual photomicrographs of the circuits - wasn't quite sure what was meant by 'pullup' - is that just a straight connection? Have you any plans to do something similar for the 68000?

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pullup resistors.

When the switch is closed, it creates a direct connection to ground or VCC, but when the switch is open, the rest of the circuit would be left floating (i.e., it would have an indeterminate voltage). For a switch that connects to ground, a pull-up resistor ensures a well-defined voltage (i.e. VCC, or logical high) across the remainder of the circuit when the switch is open. Conversely, for a switch that connects to VCC, a pull-down resistor ensures a well-defined ground voltage (i.e. logical low) when the switch is open.

https://en.m.wikipedia.org/wiki/Pull-up_resistor

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