Author: Robert Hyatt
Date: 12:52:55 07/22/03
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On July 22, 2003 at 15:48:08, Eugene Nalimov wrote: >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 I didn't use Google. I just pulled out the original alpha architecture guide. :) I can even pull out an original TI ASC guide if someone is interested in details of that 1970's era super-computer. :) > >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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