Author: Robert Hyatt
Date: 11:40:13 06/04/98
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On June 04, 1998 at 14:30:31, Tom Kerrigan wrote: >On June 03, 1998 at 19:52:54, Robert Hyatt wrote: > >>>Not true... It's been used successfully in a number of supercomputers. >>>The idea has been around and worked for 20+ years now. In fact, back >>>when RISC was coming to light, there was a fairly large-scale RISC vs. >>>VLIW controversy. >>none that I know of. IE not in Cray, CDC, Hitachi, Fujitsu, texas >>instruments, etc... ergo I know of *no* successful VLIW computers by >>anyone. just prototypes here and there... > >Well, the success of a supercomputer is hard to measure. With the Intel >supercomputer, it only sold one, but it could be said that it was fairly >successful. I was working at HP back when these questions were being >asked, and because of that, I know that there were two (maybe more) >supercomputers based on VLIW made in the 80's alone. You're right, none >of the big names built them, but they were built all the same, and from >what I gather, they were reasonably successful. > maybe we need to define successful. I go with two measures, overall performance, and overall sales. Cray is/was/will be clearly number one. They make and have generally always have made the fastest computer in the world, non-VLIW. And on sales they walk away frm everyone with over 250 installations several years ago. Not to mention current delivery times booked up to 2 years into the future. >>>>magnifying glass, it is simply a restricted form of superscalar, as was >>>Yes, it's quite clearly superscalar, and sort of "restricted," but at >>>the same time, it simplifies chip design extrordinarily, leaving die >>>space for more execution units, more cache, whatever. >>no argument there... but it puts the difficult work off onto the >>compiler, >>since it has to be done somewhere. And doing this affects binary >>compatibility in horrible ways... much nicer to have a family of > >These are simply problems to solve, but not reason to scrap the entire >idea... > >Cheers, >Tom yes.. but the problems have been solved. That was what super-scalar was all about originally. where you could have the equivalent of a "SIW", "MIW", "LIW" and "VLIW" type architectures, simply by designing your processor to fetch one, two, three or N words at a time. That's the wonderful part of super-scalar architectures.. they take old binary apps and run them faster. And when you "pool" instructions you don't even need the compiler's assistance in pairing up instructions for simultaneous issue.
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