escape-sequencing) is commonly used in instruction sets, in an arbitrary
and ad-hoc fashion, added often on an on-demand basis. Examples include:
-* Setting a SPR to switch the meaning of certain opcodes for Little-Endian
-/ Big-Endian behaviour (present in POWER and SPARC) * Setting a SPR to
-provide "backwards-compatibility" for features from older versions of
-an ISA (such as changing to new ratified versions of the IEEE754 standard)
+* Setting a SPR to switch the meaning of certain opcodes for Little-Endian /
+ Big-Endian behaviour (present in POWER and SPARC)
+* Setting a SPR to provide "backwards-compatibility" for features from
+ older versions of an ISA (such as changing to new ratified versions of
+ the IEEE754 standard)
+
+(These we term "ISA Muxing" because, ultimately, they are extra bits
+(or change existing bits) in the actual instruction decoder phase,
+which involves "MUXes" to switch them on and off).
The Libre-SOC team, developing a hybrid CPU-VPU-GPU, needs to add
significantly and strategically to the POWER ISA to support, for example,