| Opcode | Instruction | Op/En | 64-Bit Mode | Compat/Leg Mode | Description | | ---------------- | ---------------- | ----- | ----------- | --------------- | -------------------------------------------------- | | 3C ib | CMP AL, imm8 | I | Valid | Valid | Compare imm8 with AL. | | 3D iw | CMP AX, imm16 | I | Valid | Valid | Compare imm16 with AX. | | 3D id | CMP EAX, imm32 | I | Valid | Valid | Compare imm32 with EAX. | | REX.W + 3D id | CMP RAX, imm32 | I | Valid | N.E. | Compare imm32 sign-extended to 64-bits with RAX. | | 80 /7 ib | CMP r/m8, imm8 | MI | Valid | Valid | Compare imm8 with r/m8. | | REX + 80 /7 ib | CMP r/m8\*, imm8 | MI | Valid | N.E. | Compare imm8 with r/m8. | | 81 /7 iw | CMP r/m16, imm16 | MI | Valid | Valid | Compare imm16 with r/m16. | | 81 /7 id | CMP r/m32, imm32 | MI | Valid | Valid | Compare imm32 with r/m32. | | REX.W + 81 /7 id | CMP r/m64, imm32 | MI | Valid | N.E. | Compare imm32 sign-extended to 64-bits with r/m64. | | 83 /7 ib | CMP r/m16, imm8 | MI | Valid | Valid | Compare imm8 with r/m16. | | 83 /7 ib | CMP r/m32, imm8 | MI | Valid | Valid | Compare imm8 with r/m32. | | REX.W + 83 /7 ib | CMP r/m64, imm8 | MI | Valid | N.E. | Compare imm8 with r/m64. | | 38 /r | CMP r/m8, r8 | MR | Valid | Valid | Compare r8 with r/m8. | | REX + 38 /r | CMP r/m8\*, r8\* | MR | Valid | N.E. | Compare r8 with r/m8. | | 39 /r | CMP r/m16, r16 | MR | Valid | Valid | Compare r16 with r/m16. | | 39 /r | CMP r/m32, r32 | MR | Valid | Valid | Compare r32 with r/m32. | | REX.W + 39 /r | CMP r/m64,r64 | MR | Valid | N.E. | Compare r64 with r/m64. | | 3A /r | CMP r8, r/m8 | RM | Valid | Valid | Compare r/m8 with r8. | | REX + 3A /r | CMP r8\*, r/m8\* | RM | Valid | N.E. | Compare r/m8 with r8. | | 3B /r | CMP r16, r/m16 | RM | Valid | Valid | Compare r/m16 with r16. | | 3B /r | CMP r32, r/m32 | RM | Valid | Valid | Compare r/m32 with r32. | | REX.W + 3B /r | CMP r64, r/m64 | RM | Valid | N.E. | Compare r/m64 with r64. | > * In64-bit mode, r/m8 cannot been coded to access the following byte registers if a REX prefix is used: AH, BH, CH, DH.