This is absolutely incredible. Check out this JavaScript simulation of an old-school MOS 6502 processor – the heart of the Commodore 64, among other computers.

These guys got a 6502 chip, decapped it with acid and took high resolution pictures of the actual chip substrate. They then ran some image processing tasks over this captured image to turn the image into a map of transistors, then took this map and used it to simulate the CPU in JavaScript.

Their simulation is accurate enough to run old games by directly emulating not the instruction set of the CPU but the physical transistors. You can step through in the simulator to see how the electric current flows around the chip, clock cycle by clock cycle. It all is so far above my head that it’s not funny, but it’s still very interesting to watch the deterministic precision of what was going on inside an old CPU and then imagine just what furious processes are happening inside the chips that power our computers today…

via www.Visual6502.org.