<a href="https:&#x2F;&#x2F;books.google.com.au&#x2F;books?id=GBXqCAAAQBAJ&amp;pg=PA28&amp;lpg=PA28&amp;dq=6502+nintendo+variant" rel="nofollow">https:&#x2F;&#x2F;books.google.com.au&#x2F;books?id=GBXqCAAAQBAJ&amp;pg=PA28&amp;lp...</a> possibly? Failing that, byuu (developer of the Higan emulator) might know.