Linked by Thom Holwerda on Tue 15th Jan 2013 22:29 UTC
"In this article, I show
at the transistor and silicon level. I've discussed the mathematics of the 6502 overflow flag earlier and thought it would be interesting to look at the actual chip-level implementation. Even though the overflow flag is a slightly obscure feature, its circuit is simple enough that it can be explained at the silicon level."