Intel 8086

From Misc Data Digs

Undocumented Instructions[edit | edit source]

POP CS[edit | edit source]

Opcode 0Fh pops the value from CS. The instruction opcode was re-used in 80286 onward.

MOV CS[edit | edit source]

Opcode 8Eh moves a value to CS.

AAM imm8[edit | edit source]

Opcode D4h imm8 divides AL by imm8, put the quotient in AH, and the remainder in AL. This is only documented starting with the Pentium (earlier documentation lists no arguments).

AAD imm8[edit | edit source]

Opcode D5h imm8 is the multiplication counterpart of the above instruction. Like the above, this instruction is only documented starting with the Pentium.

SALC/SETALC[edit | edit source]

Opcode D6h is an instruction where register AL is set to either 0h or FFh depending on what the carry flag is set to. While this instruction is on all future x86 architectures, it remained undocumented by Intel until 2017.