[kazinator]

But "undefined ops" are not part of the "8080 instruction set"; supporting those would be "binary compatible with the 8080 silicon".

The parity flag is a breaker though; "binary compatible for code only relying on the 8080 instruction set, other than values of the parity flag".

[Zardoz84]

By the same thinking that have the parent post The 80286 and 80386 aren't binary compatible with the 8086. Because they replaced undefined opcodes with new stuff.