Bunnie writes -

This has to be one of the coolest retro-hardware projects I’ve seen in a while. It’s a transistor-level simulator of the 6502, written in Javascript, that visually simulates the device based on its original mask pattern — painstakingly reverse-engineered from high-resolution die photographs. Fortunately, mask works have a “sane” copyright term of only a decade, so cool projects like this are facilitated through such reasonable limitations on copyright lifetimes.

…As it runs, the wires dynamically change color on a cycle-by-cycle basis as the logic states of each wire update.

It makes my head spin to think that the CPU from the first real computer I used, the Apple II, is now simulateable at the mask level as a browser plug-in. Nothing to install, and it’s Open-licensed. How far we have come…a little more than a decade ago, completing a project like this would have resulted in a couple PhDs being awarded, or regarded as trade secret by some big EDA vendor. This is just unreal…but very cool!