| Opcode | Instruction | Op/En | 64-Bit Mode | Compat/Leg Mode | Description |
| 0C ib | OR AL, imm8 | I | Valid | Valid | AL OR imm8. |
| 0D iw | OR AX, imm16 | I | Valid | Valid | AX OR imm16. |
| 0D id | OR EAX, imm32 | I | Valid | Valid | EAX OR imm32. |
| REX.W + 0D id | OR RAX, imm32 | I | Valid | N.E. | RAX OR imm32 (sign-extended). |
| 80 /1 ib | OR r/m8, imm8 | MI | Valid | Valid | r/m8 OR imm8. |
| REX + 80 /1 ib | OR r/m8*, imm8 | MI | Valid | N.E. | r/m8 OR imm8. |
| 81 /1 iw | OR r/m16, imm16 | MI | Valid | Valid | r/m16 OR imm16. |
| 81 /1 id | OR r/m32, imm32 | MI | Valid | Valid | r/m32 OR imm32. |
| REX.W + 81 /1 id | OR r/m64, imm32 | MI | Valid | N.E. | r/m64 OR imm32 (sign-extended). |
| 83 /1 ib | OR r/m16, imm8 | MI | Valid | Valid | r/m16 OR imm8 (sign-extended). |
| 83 /1 ib | OR r/m32, imm8 | MI | Valid | Valid | r/m32 OR imm8 (sign-extended). |
| REX.W + 83 /1 ib | OR r/m64, imm8 | MI | Valid | N.E. | r/m64 OR imm8 (sign-extended). |
| 08 /r | OR r/m8, r8 | MR | Valid | Valid | r/m8 OR r8. |
| REX + 08 /r | OR r/m8*, r8* | MR | Valid | N.E. | r/m8 OR r8. |
| 09 /r | OR r/m16, r16 | MR | Valid | Valid | r/m16 OR r16. |
| 09 /r | OR r/m32, r32 | MR | Valid | Valid | r/m32 OR r32. |
| REX.W + 09 /r | OR r/m64, r64 | MR | Valid | N.E. | r/m64 OR r64. |
| 0A /r | OR r8, r/m8 | RM | Valid | Valid | r8 OR r/m8. |
| REX + 0A /r | OR r8*, r/m8* | RM | Valid | N.E. | r8 OR r/m8. |
| 0B /r | OR r16, r/m16 | RM | Valid | Valid | r16 OR r/m16. |
| 0B /r | OR r32, r/m32 | RM | Valid | Valid | r32 OR r/m32. |
| REX.W + 0B /r | OR r64, r/m64 | RM | Valid | N.E. | r64 OR r/m64. |
Notes: * In 64-bit mode, r/m8 can not be encoded to access the following byte registers if a REX prefix is used: AH, BH, CH, DH.
| Op/En | Operand 1 | Operand 2 | Operand 3 | Operand 4 |
| I | AL/AX/EAX/RAX | imm8/16/32 | NA | NA |
| MI | ModRM:r/m (r, w) | imm8/16/32 | NA | NA |
| MR | ModRM:r/m (r, w) | ModRM:reg (r) | NA | NA |
| RM | ModRM:reg (r, w) | ModRM:r/m (r) | NA | NA |
Performs a bitwise inclusive OR operation between the destination (first) and source (second) operands and stores the result in the destination operand location. The source operand can be an immediate, a register, or a memory location; the destination operand can be a register or a memory location. (However, two memory operands cannot be used in one instruction.) Each bit of the result of the OR instruction is set to 0 if both corresponding bits of the first and second operands are 0; otherwise, each bit is set to 1.
This instruction can be used with a LOCK prefix to allow the instruction to be executed atomically.
In 64-bit mode, the instruction’s default operation size is 32 bits. Using a REX prefix in the form of REX.R permits access to additional registers (R8-R15). Using a REX prefix in the form of REX.W promotes operation to 64 bits. See the summary chart at the beginning of this section for encoding data and limits.
DEST ← DEST OR SRC;
The OF and CF flags are cleared; the SF, ZF, and PF flags are set according to the result. The state of the AF flag is undefined.
| #GP(0) | If the destination operand points to a non-writable segment. If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If the DS, ES, FS, or GS register contains a NULL segment selector. |
| #SS(0) | If a memory operand effective address is outside the SS segment limit. |
| #PF(fault-code) | If a page fault occurs. |
| #AC(0) | If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3. |
| #UD | If the LOCK prefix is used but the destination is not a memory operand. |
| #GP | If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. |
| #SS | If a memory operand effective address is outside the SS segment limit. |
| #UD | If the LOCK prefix is used but the destination is not a memory operand. |
| #GP(0) | If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. |
| #SS(0) | If a memory operand effective address is outside the SS segment limit. |
| #PF(fault-code) | If a page fault occurs. |
| #AC(0) | If alignment checking is enabled and an unaligned memory reference is made. |
| #UD | If the LOCK prefix is used but the destination is not a memory operand. |
Same as for protected mode exceptions.
| #SS(0) | If a memory address referencing the SS segment is in a non-canonical form. |
| #GP(0) | If the memory address is in a non-canonical form. |
| #PF(fault-code) | If a page fault occurs. |
| #AC(0) | If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3. |
| #UD | If the LOCK prefix is used but the destination is not a memory operand. |