Modern intel CPUs can decide 4 instructions per cycle. 9 single byte nops in a row would therefore take 3 cycles (though the last cycle will overlap with upto 3

Modern intel CPUs can decide 4 instructions per cycle. 9 single byte nops in a row would therefore take 3 cycles (though the last cycle will overlap with upto 3 more instructions.) A multibyte nop counts as one instruction, taking just one cycle to decode, and leaving room for upto 3 more instructions to decode that cycle.