* On GBZ80, RETI automatically performs an EI. The Z80 does not. [https://rgbds.gbdev.io/docs/master/gbz80.7#RETI Source]
* STOP is normally a 2-byte instruction where the second byte is ignored. [https://gbdev.io/pandocs/Reducing_Power_Consumption.html#using-the-stop-instruction Source]
* STOP is used on Gameboy Color to switch between normal speed and double speed CPU modes.
* RST instructions are just a CALL instruction to a fixed address baked in the instruction itself.
* Despite what the syntax of the instructions JP (HL/IX/IY) suggests, PC will be loaded with the contents of the register itself, not the indexed value. Those instructions should be understood as JP HL/IX/IY.