> > > So apparently MIPS_ATOMIC_SET was invented for Linux only, probably just to > > > implement _test_and_set(). (It would be interesting to see how IRIX implement > > > _test_and_set() on MIPS I machines. However, the machine I have access uses > > > ll/sc instructions). > > > > Does IRIX actually run on anything below ISA II? > > > > I assume nobody answering the above questions means nobody > really care. So we can safely move ahead without worrying about > them. :-) I was waiting for someone to give a more authoritative answer, but IIRC from my days at SGI, IRIX did of course run on the R3000-based products, but support for them was dropped in IRIX 6.x. I couldn't give you the version number of the last IRIX version that did support the R3K, though. And as others have observed, it was in any case not IRIX, but MIPS' own RiscOS that drove the ABI. Keivn K.