SVP64 is designed so that when the prefix is all zeros, no effect or
influence occurs (no augmentation) such that all standard OpenPOWER
-v3.B instructions may be active at that time, in full (and SV is
-quiescent). The corollary is that when the SV prefix is nonzero,
-alternative meanings may be given to all and any instructions.
+v3.0/1B instructions are "unaltered". This is termed `scalar identity behaviour` (based on the mathematical definition for "identity", as in, "identity matrix")
# Definition of Reserved in this spec.