| Opcode     | Instruction | Op/En | 64-bit Mode | Compat/Leg Mode | Description                |
| ---------- | ----------- | ----- | ----------- | --------------- | -------------------------- |
| 98         | CBW         | ZO    | Valid       | Valid           | AX := sign-extend of AL.   |
| 98         | CWDE        | ZO    | Valid       | Valid           | EAX := sign-extend of AX.  |
| REX.W + 98 | CDQE        | ZO    | Valid       | N.E.            | RAX := sign-extend of EAX. |