Path: utzoo!utgpu!news-server.csri.toronto.edu!eecg.toronto.edu!leblanc
Newsgroups: comp.sys.amiga.hardware
From: leblanc@eecg.toronto.edu (Marcel LeBlanc)
Subject: Re: RISC Amiga
Message-ID: <1990Oct31.012758.26467@jarvis.csri.toronto.edu>
Keywords: A RISC Mac?  So what?
References: <1156@iceman.jcu.oz> <1990Oct30.173846.6928@idt.unit.no>
Date: 31 Oct 90 06:27:58 GMT
Lines: 37

daglem@solan.unit.no (Dag Lem) writes:

>In article <1156@iceman.jcu.oz>, cpca@iceman.jcu.oz (C Adams) writes:
>|> So what would we want a RISC Amiga to be based on, 88k? Sparc? i860? MIPS?
>|> What about compatibility with existing software? 
>|> 
>We don't want a RISC amiga! Software compatibility? Are you joking?
> If you want speed, opt for a 68040. It may do fewer MIPS than RISCS, but
> that's NOT the way to compare 68040 with RISCS (or any other processor, for
> that matter).  The 68000 series can perform rather complex operations with
> one instruction. Most RISCS do virtually nothing with one instruction. Guess
> you've been reading too many ads stating '..running at xx MIPS! Compare this
> to ..' :-)

Here we go again.  Guess you've been reading too many BYTE pseudo-technical
articles again.  The whole point to the RISC approach to processor (and
system) design is to implement only instructions that are used, and to make
those instructions as fast as possible.  The 'rather complex operations'
performed by CISC are usually a waste of silicon because they aren't used.
And the notion that RISCs "do virtually nothing with one instruction" will
certainly be news to the designers of the MIPS R3000, who worked very hard
to get the 'cycles per (useful) instruction' as close to 1.0 as possible!
In fact, the R3000 achieves 1.27 clocks/SPEC integer.  You can be sure this
is better than what the 68040 (certainly the FASTEST of the 68K line) can
achieve, because Motorola's predicted performance for the 68040 isn't evenb
that high.  And Motorola's 'performance predictions' are claims that have yet
to be proven.

>    __                /                       |> Shorter of breath
>   /  \  __   __     /   ___  _ _             |> and one day closer to death.
>  /    |/  / /  /   /   /__/ / / /            |>   -Roger Waters, Time 
> /____/ \_/|/\_/   /____\___/ /  \__________  |>    (Dark Side of The Moon) 
>______________/

Marcel A. LeBlanc  --  Electrical Eng. Computer Group, Univ. of Toronto
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