What is the maximum length an Intel 386 instructio

问题:

I have read this answer, but I need to know what is the longest instruction length on Intel 386(which is 32-bit not 64 bit) without using any instruction prefixes.

Based on the manual, it is probably 12:

• Opcode: 2 bytes
• MOD/Rm: 1 byte
• SIB: 1 byte
• Displacement: 4 bytes
• Immediate: 4 bytes
• Total: 12

Is this the correct answer?

回答1:

On 80386 that would be 11 bytes:

• Opcode: 1 byte
• MOD/RM: 1 byte
• SIB: 1 byte
• Displacement: 4 bytes
• Immediate: 4 bytes

The 2-byte opcodes are using the 0Fh instruction prefix which obviously is a prefix.