Author: Eugene Nalimov
Date: 12:48:08 07/22/03
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Is it necessary to use the word "ass" when the person whom you are talked with is polite? Regarding Alpha: yes, it had conditional move from day one. BTW, HP-PA has instruction nullification before that. And you are right, conditional execution (or some form of conditional "skip" instruction) was invented long before that. But: when earlier Bob wrote something from memory you wrote "why you didn't use google? I used it and found the result immediately". Can you please *yourself* either use your own advice, or do not cruely attack others when they are doing exactly what you are doing? Thanks, Eugene On July 22, 2003 at 15:02:46, Tom Kerrigan wrote: >On July 22, 2003 at 14:18:23, Robert Hyatt wrote: > >>>Of course, this is contrary to the point of a conditional move instruction. My >>>only comment to that is that Intel must have decided to add the conditional move >>>after they were done designing the relevant parts of the core. The decision to >>>add the instruction makes sense for forward-compatibility, i.e., "use this >>>instruction and you will see a performance improvement with it on later >>>processors." >> >>That could be. However, the idea was not new. The alpha did this 10+ years >>ago. So the advantage to a real CMOV implementation should be real. > >Did I ever say it was new? Did I say that Intel's implementation is ideal? No, I >didn't. And conditional move is just a poor man's predication, which has been >implemented in processors LONG before Alpha. (And, IIRC, conditional move was a >recently added Alpha instruction. I don't think it was in the 21064.) > >I see nothing wrong with what Intel did. If my hunch is right and they only >thought of adding the instruction after the P6 datapaths were planned/designed, >then the net effect is that they added an instruction that doesn't increase >performance, or increases it only marginally. So it's a little something extra >they threw in there to future-proof the processor which isn't hurting you >because you DON'T EVEN HAVE TO USE IT. So you're being an ass for criticizing >them for it. They could have just as easily left it out and then you would have >had no complaints. > >-Tom
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