> That's 47 years ago, not 57. > F00F bug? ;-) For those who are out of the loop: https://en.wikipedia.org/wiki/Pentium_F00F_bug https://en.wikipedia.org/wiki

> That's 47 years ago, not 57. > F00F bug? ;-) For those who are out of the loop: https://en.wikipedia.org/wiki/Pentium_F00F_bug https://en.wikipedia.org/wiki/Pentium_F00F_bug Though since your parent was talking about the Intel 8086/8088 and 0x0F: There is an incompatibility 8086/8088 and newer x86 processors: On Intel 8086/8088 the opcode 0x0F was "pop cs". From 80186/80188 on, 0x0F is instead an opcode expansion prefix (cf. https://stackoverflow.com/a/12264515/497193 https://stackoverflow.com/a/12264515/497193).