Viestissä Maanantai 21. Lokakuuta 2002 13:18, Mike A. Harris kirjoitti: > On Mon, 21 Oct 2002, Andrew Smith wrote: > >Interesting if you take that to the next step - it means that there > >are NO extra useful instruction or optimisations in a 486 or a > >Pentium (586) procesor over a 386 processor (...) > Well, there are new instructions in i486, and i586, however most > of them just are not useful in general purpose code. The optimizations for i586 aren't related to instruction set, but to instruction scheduling. Pentium is a dual-issue superscalar CPU without out-of-order execution. This means that the compiler needs to carefully arrange the instruction stream to keep both pipelines busy, and sometimes even insert NOPs in the instruction stream. This causes code that's optimally scheduled for i586 to run slower both on single-pipeline CPUs like i386 and i486, and more advanced superscalar CPUs like i686 and Athlon. -- Markku Kolkka markku.kolkka@koti.soon.fi -- Psyche-list mailing list Psyche-list@redhat.com https://listman.redhat.com/mailman/listinfo/psyche-list
