* ADD HL,ss takes 2 cycles on the GBZ80, but 3 NOPs on the Z80
Flags can differ too: * DAA clears HF in the GBZ80, but not in the Z80
* RLCA, RRCA, RLA, RRA clear ZF in the GBZ80, but not in the Z80
* DAA clears HF in the GBZ80, but not in the Z80
Fun fact: Way more GBZ80 cores were produced for Gameboy hardware (118 million Gameboys and 81 million GBA) than all the Z80 chips produced for home computers and game consoles. [https://www.chibiakumas.com/z80/Gameboy.php Learn GBZ80 Assembly Programming with ChibiAkumas]