order for encoding x86 instruction prefix bytes

Question

I know that x86 instructions can have a maximum of 4 bytes of prefixes, e.g Lock, rep, segment overrides etc.

Is there any particular order in which they should appear,

Answer 1

the order can be found in volume 2A of the Intel Software Developer's Manual.

In a nutshell:

• the F2 and F3 prefixes cancel each other out. The one that comes later has precedence.
• the 66 prefix is ignored if either F2 or F3 are used (as mandatory prefixes in a long instruction). This of course doesn't apply to rep movsw where both those prefixes are simply prefixes, not part of the opcode.
• the REX escape may not be followed by any other prefixes.
• the VEX escape may not be preceded by REX, 66, F2 or F3

for the rest, the order shouldn't matter.