There's actually several official nops on x86, each of different instruction length. To be fair, I think they back ported this behavior to the official arch af

There's actually several official nops on x86, each of different instruction length. To be fair, I think they back ported this behavior to the official arch after Microsoft relied on it. AMD defines up to 11 byte sequeces, Intel defines up to 9 byte sequences. 90 NOP 6690 66 NOP 0f1f00 NOP DWORD ptr [EAX] 0f1f4000 NOP DWORD ptr [EAX + 00H] 0f1f440000 NOP DWORD ptr [EAX + EAX*1 + 00H] 660f1f440000 66 NOP DWORD ptr [EAX + EAX*1 + 00H] 0f1f8000000000 NOP DWORD ptr [EAX + 00000000H] 0f1f840000000000 NOP DWORD ptr [EAX + EAX*1 + 00000000H] 660f1f840000000000 66 NOP DWORD ptr [EAX + EAX*1 + 00000000H] 66660f1f840000000000 66 66 NOP DWORD ptr [EAX + EAX*1 + 00000000H] 6666660f1f840000000000 66 66 66 NOP DWORD ptr [EAX + EAX*1 + 00000000H] https://stackoverflow.com/questions/25545470/long-multi-byte-nops-commonly-understood-macros-or-other-notation https://stackoverflow.com/questions/25545470/long-multi-byte...