32-bit instructions require a prefix-marker bit, it does effectively
double the **entirety** of the 32-bit Major Opcode space.
+Section 1.6.3:
+
+```
+Prefix bits 6:7 are used to identify one of four prefix for-
+mat types. When bit 6 is set to 0 (prefix types 00 and
+01), the suffix is not a defined word instruction (i.e.,
+requires the prefix to identify the alternate opcode
+space the suffix is assigned to as well as additional or
+extended operand and/or control fields); when bit 6 is
+set to 1 (prefix types 10 and 11), the prefix is modifying
+the behavior of a defined word instruction in the suffix.
+```
+
this "doubling" is already public and part of EXT001, the idea
here is to mirror that (bit 6), but unlike EXT001, use bit 7
to mark whether the instruction is SVP64-vector or SVP64-single.