Discrete logic circuits can be fast because they have a lot of area over which to dissipate heat and can guzzle current. Moreover, most of them used either ECL

Discrete logic circuits can be fast because they have a lot of area over which to dissipate heat and can guzzle current. Moreover, most of them used either ECL or TTL, which are logic families much faster than P/N/CMOS. This being a transistor-level replica of an NMOS 6502, it can't go much faster.