Excerpts from Segher Boessenkool's message of May 25, 2022 4:32 am: > On Tue, May 24, 2022 at 11:52:00AM +0200, Florian Weimer wrote: >> * 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. > > Linux runs on ISA 1.xx and ISA 2.01 machines still. "Category" wasn't > invented for either yet either, but similar concepts did exist of > course.
Not sure what to say about this. It now also has "Compliancy Subset" although maybe that's more like a set of features rather than incompatible features or modes such as some of the category stuff seems to be. I'll try add something. Thanks, Nick