Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!dali.cs.montana.edu!uakari.primate.wisc.edu!sdd.hp.com!cs.utexas.edu!wuarchive!uunet!bywater!scifi!watson!arnor!prener!prener From: prener@watson.ibm.com (Dan Prener) Newsgroups: comp.arch Subject: Re: Scalar vs Superscalar Message-ID: <1991May8.002205.19717@watson.ibm.com> Date: 8 May 91 00:22:05 GMT References: <1991May6.152803.5886@midway.uchicago.edu> Sender: news@watson.ibm.com (NNTP News Poster) Reply-To: prener@prener.watson.ibm.com (Dan Prener) Organization: IBM T.J. Watson Research Center Lines: 27 Nntp-Posting-Host: prener In article <1991May6.152803.5886@midway.uchicago.edu>, rtp1@quads.uchicago.edu (raymond thomas pierrehumbert) writes: |> I have often heard the HP snake machines described as "not superscalar" |> whereas the IBM RS/6000 are generally described as "superscalar." |> What is it in the architectures of these two machines that supports |> this distinction? What are the consequences for the kinds of codes |> that will run efficiently (particularly in terms of floating point |> performance)? |> |> (P.S. could somebody email me a definition of "little endian" vs. |> "big endian" ? Are RS6000's, Suns and Macintoshes "big endian"? |> What about i860? Is it a property of the chip, or of the OS?) Although one could concoct counterexamples, as normally used today "superscalar" and "superpipelined" describe machine implementations, not architectures. ------------------------------ A brief characterization of "little/big endian" is the following. Suppose your machine computes the (hex) integer 0x12345678 in a 32 bit register. And suppose it then stores the contents of that register into bytes zero through three in memory. If the byte at memory location zero contains 0x12, it is a big-endian machine. If the byte at location zero contains 0x78, it is a little-endian machine. As usual this is oversimplified. The full truth is more complicated and considerably uglier. -- Dan Prener (prener @ watson.ibm.com)