It makes more sense if you look at the neighbors on the opcode map. It seems like the range 0x90-0x97 are all variants of xchg, just that the first happens to h

It makes more sense if you look at the neighbors on the opcode map. It seems like the range 0x90-0x97 are all variants of xchg, just that the first happens to have a destination same as source: http://sparksandflames.com/files/x86InstructionChart.html http://sparksandflames.com/files/x86InstructionChart.html