as a new 64-bit encoding space, alongside Primary Opcode 1
(EXT1xx).
-| 0-5 | 6 | 7 | 8-31 | 32| Description |
-|-----|---|---|-------|---|------------------------------------|
-| PO | 0 | x | xxxx | 0 | `RESERVED2` (57-bit) |
-| PO | 0 | 0 | !zero | 1 | SVP64Single:EXT232-263, or `RESERVED3` |
-| PO | 0 | 0 | 0000 | 1 | Scalar EXT232-263 |
-| PO | 0 | 1 | nnnn | 1 | SVP64:EXT232-263 |
-| PO | 1 | 0 | 0000 | x | `RESERVED1` (32-bit) |
-| PO | 1 | 0 | !zero | n | SVP64Single:EXT000-063 or `RESERVED4` |
-| PO | 1 | 1 | nnnn | n | SVP64:EXT000-063 |
+| 0-5 | 6 | 7 | 8-31 | 32|33-63|Description |
+|-----|---|---|-------|---|-----|-----------------------------------|
+| PO9 | 0 | x | xxxx | 0 | xxxx| `RESERVED2` (57-bit) |
+| PO9 | 0 | 0 | !zero | 1 | DWd | SVP64Single:EXT232-263, or `RESERVED3` |
+| PO9 | 0 | 0 | 0000 | 1 | DWd | Scalar EXT232-263 |
+| PO9 | 0 | 1 | nnnn | 1 | DWd | SVP64:EXT232-263 |
+| PO9 | 1 | 0 | 0000 | x | xxxx| `RESERVED1` (32-bit) |
+| PO9 | 1 | 0 | !zero | n | DWd | SVP64Single:EXT000-063 or `RESERVED4` |
+| PO9 | 1 | 1 | nnnn | n | DWd | SVP64:EXT000-063 |
+
+Key:
+
+* **x** - a `RESERVED` encoding. Illegal Instruction Trap must be raised
+* **n** - a specification-defined value
+* **!zero** - a non-zero specification-defined value
+* **DWd** - "Defined Word" as explained in Book I Section 1.6 (Public v3.1 p11)
Note that for the future SVP64Single Encoding (currently RESERVED3 and 4)
it is prohibited to have bits 8-31 be zero, unlike for SVP64 Vector space,
for which bits 8-31 can be zero (termed `scalar identity behaviour`). This
prohibition allows SVP64Single to share its Encoding space with Scalar
-Ext232-263 and Scalar EXT300-363.
+EXT232-263 and Scalar EXT300-363.
Also that RESERVED1 and 2 are candidates for future Major opcode
areas EXT200-231 and EXT300-363 respectively, however as RESERVED areas