On Sat, Nov 24, 2012 at 12:47:01PM +0100, Jonas Bonn wrote: > On Sat, 2012-11-24 at 12:16 +0200, Stefan Kristiansson wrote: > > On Sat, Nov 24, 2012 at 09:51:21AM +0100, Jonas Bonn wrote: > > > Reading back 0 for non-existant regs is "nice", but I don't immediately > > > see the advantage of 0 over "random garbage"... I would go as far as to > > > saying saying "unused SPR space reads back undefined value", but there's > > > possibly a 'hardware' advantage to not doing so..??? > > > > > > > I believe the advantage of having 'unused spr' read back as 0 > > really started as 'reserved for future use spr' read back as 0. > > And the advantage of that is of course that they then have a known > > 'before' value when they are taken into use in the future. > > > > Are you sure you're not confusing "undefined bits in defined SPR" and > "undefined SPR"? I'd say the former warrants reading back 0, while the > latter wants a feature bit. >
Not sure at all ;) In other words, I agree. Stefan _______________________________________________ OpenRISC mailing list [email protected] http://lists.openrisc.net/listinfo/openrisc
