* While the syntax of ADD, ADC and SBC instructions all explicitly mention the A register, the SUB instruction does not mention it. On the Zilog eZ80, the SUB instruction explicitly mention the A register.
* IN r,(C) and OUT (C),r instructions syntax is misleading as these instructions actually use the full 16-bit port address contained in BC. On the Zilog eZ80, these instructions are correctly named IN, r,(BC) and OUT (BC),r.
* The Amstrad engineers chose to use the high byte of the address (register B) for chip selection instead of the low byte (register C) in I/O operations. As a result, the Amstrad CPC cannot use interesting instructions like OTIR / OTDR / INIR / INDR cannot be used on Amstrad CPC for transferring or reading a sequence of values on a port as they use B as a counter.
* The 16-bit commands ADD HL,ss, ADC HL,ss and SBC HL,ss exist but not the command SUB HL,ss.
* All PUSH and POP instructions utilize a 16-bit operand and the high-order byte is always pushed first and popped last. PUSH HL is PUSH H then L. POP HL is POP L then H.