Having recently replayed this classic game and then completing all the “homework” from this excellent book, I was left wondering how things really work down at the silicon level. The game I’m sure is a much simplified version of reality, and the book starts at the level immediately above the game. I looked at a few Wikipedia pages and whatever “Electronics 101″ class notes I could find, but all I managed to learn is that in the real world 1) everything needs to be grounded and 2) resistors are involved somehow? I think?
All that said, when I found this blog post by Ken Shirriff today, it was as if it was made just for me! The post zooms in on the actual silicon of the 6502 processor, showing in detail exactly how the overflow flag is calculated. Ever used an Apple II or an Atari 2600? These microscopic wires lit up every time the processor added two numbers.
So from the book, I know how to build an entire computer using only NAND gates. And now from this blog post, I KNOW HOW TO MAKE NAND.