Visual6502wiki/Balazs' schematic and documents
Beregnyei Balazs (family name first!) derived a schematic from his die photo and wrote up notes on the circuits.
The chip is an R6502 which is a Rockwell part but uses MOS Technology’s masks.
Henry S. Courbis worked with a friend of Balazs on an English translation
- Beregnyei Balazs: 6502 Reverse Engineering directory (archived)
- translated documents directory: Doc and pdf.
- single page schematic 730kByte pdf
Balazs gave a 40 minute presentation on the reverse engineering at Hacktivity 2011, see here (original Hungarian) and here (English voiceover).