3 ms·
Yup, that's POP CS, 0x0f. Since it made no sense to use, it became the way 286 and later processors used to indicate multibyte opcodes. When a 286 is running
by hota_mazi 3y ago
Yup, that's POP CS, 0x0f.
Since it made no sense to use, it became the way 286 and later processors used to indicate multibyte opcodes.
When a 286 is running the code, encountering a 0x0f means that the following opcode is multibyte, while on an 8088, all opcodes are single bytes.
- cesarb 3y ago> while on an 8088, all opcodes are single bytes. According to a recent article on undocumented 8086/8088 opcodes (https://www.righto.com/2023/07/undocumented-8086-instructions.html https://www.righto.com/2023/07/undocumented-8086-instruction...), there are some two-byte opcodes: "For most of the 8086 instructions, the first byte specifies the instruction. However, the 8086 has a few instructions where the second byte specifies the instruction: the reg field of the ModR/M byte provides an opcode extension that selects the instruction."