The article mentions a "6502.7" CPU core that Ricoh had. I don't think I've ever heard of this designation before, and Google doesn't seem to find any relevant hits other than this article. Does anyone know something about it? I guess it's probably just an internal designation for a specific layout variation/revision, but it seems like it might be a new detail.

https://books.google.com.au/books?id=GBXqCAAAQBAJ&pg=PA28&lp... possibly? Failing that, byuu (developer of the Higan emulator) might know.

This is _really_ a great book btw. It was one of the few things keeping me sane on a bad business trip.

The Ricoh part (2A03) is a 6502 core with BCD instructions deactivated (not removed) so Ricoh didn't have to pay patent royalties.

It may even just be a SKU for guaranteeing certain spec tolerances requested by Nintendo, or a minor variation in final trim specifications.

@tanakah (Twitter handle) might know something about it, since he wrote one of the earliest NES emulator implementations.

The 6502 core in the 2A03 and 2A07 is the only I know of that had the BCD support removed, which reduced licensing fees as the BCD circuitry was the only patented part of the 6502. That's my guess as to the meaning of the ".7"