Prefixed-Prefixed-instructions (SVP64 Prefixed v3.1 Prefixed)
would become a whopping 96-bit long instruction. Avoiding this
situation is a high priority which in turn by necessity puts pressure
-on the 32-bit Major Opcode space. Alternative locations for SVP64
-Prefixing include EXT006 and EXT017, with EXT006 being most favourable.
+on the 32-bit Major Opcode space.
SVP64 itself is already under pressure, being only 24 bits. If it is
not permitted to take up 25% of EXT001 then it would have to be proposed
requiring two Major opcodes this would come to a grand total of 3 precious
Major opcodes. On balance, then, sacrificing 25% of EXT001 is the "least
difficult" choice.
+Alternative locations for SVP64
+Prefixing include EXT006 and EXT017, with EXT006 being most favourable
+as there is room for future expansion.
Note also that EXT022, the Official Architectural Sandbox area
available for "Custom non-approved purposes" according to the Power