Article View: comp.arch
Article #1941Re: Superscalar ISAs
From: Stan Lackey
Date: Wed, 23 Aug 1989 17:34
Date: Wed, 23 Aug 1989 17:34
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In article <1989Aug22.212330.8119@stellar.COM> sporer@stellar.com writes: >We at Stellar designed our own ISA which has lots of RISC characteristics: >We did extend the RISC ideas >by incorporating memory operates, complex addressing (effective addressing >in the operates as well as load/store), and the incorporation of vector >operations and concurrency operations. >that not all our functional units were busy all the time so we added a >feature called packetization - which the industry now calls superscalar. >However, after much work, we found that we only get a 10 percent increase >in overall performance. We can packetize 2 integer, or 2 fp (a + and a *), >or 1 fp and 1 integer. You already have 90%? of what 'superscalar' gets in your instruction set: mem-to-reg operations, complex addressing, and vectors. Now, a true RISC doesn't have those features, and so they will see very significant improvements. Go ahead and flame me, but that's why I say that superscalar and CISC get the same thing, but in slightly different ways. Sure, superscalar is more general and according to what I get from the posting 10% better than CISC. But it can be more expensive, depending upon issues like backwards compatibility. -Stan
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Path: arc1-ca.pugleaf.net!utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.csd.uwm.edu!bbn!bbn.com!slackey From: slackey@bbn.com (Stan Lackey) Newsgroups: comp.arch Subject: Re: Superscalar ISAs Message-ID: <44677@bbn.COM> Date: 23 Aug 89 17:34:18 GMT References: <1989Aug22.212330.8119@stellar.COM> Sender: news@bbn.COM Reply-To: slackey@BBN.COM (Stan Lackey) Organization: Bolt Beranek and Newman Inc., Cambridge MA Lines: 23