Nice set of articles: flagged as toread.

One quick note: with the visual6502 project (http://www.visual6502.org/), and the c-implementation (https://github.com/mist64/perfect6502), a fun way to test your emulator timing is to run it in parallel with the gate-level simulation, and compare them. For example, I do this with my golang 6502 emulator: https://github.com/zellyn/go6502/blob/master/tests/compare_t...