* Nicholas Piggin: > +2. Facilities > +------------- > +The Power ISA uses the term "facility" to describe a class of instructions, > +registers, interrupts, etc. The presence or absence of a facility indicates > +whether this class is available to be used, but the specifics depend on the > +ISA version. For example, if the VSX facility is available, the VSX > +instructions that can be used differ between the v3.0B and v3.1B ISA > +verstions.
The 2.07 ISA manual also has categories. ISA 3.0 made a lot of things mandatory. It may make sense to clarify that feature bits for mandatory aspects of the ISA are still set, to help with backwards compatibility. Thanks, Florian
