Posted by dbreunig 18 hours ago
Did they test every possible input/output combination?
But to answer your question, it's in the readme: https://github.com/dbreunig/nesformer#how-it-was-checked
No, because that would be impossible.
You perform a series of more specific tests. In this case, it's "working" in so far as that Super Mario Bros. appears to be playable, for example.
Does not mean that it behaves perfectly according to some spec, or identical to another CPU (like the NES's 6502), of course, but it's clearly a working CPU to some 6502-compatible extent.
But my point was exactly that the (extremely vastly) smaller subset of tests that you performed is more than enough to proclaim a CPU to be “working”.
There was a real risk of their trademark getting Kleenex'd, at least in the US.
