Path: utzoo!attcan!uunet!wuarchive!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!nuug!sigyn.idt.unit.no!solan5.solan.unit.no!daglem
From: daglem@solan5.solan.unit.no (Dag Lem)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: RISC Amiga
Keywords: A RISC Mac?  So what?
Message-ID: <1990Oct31.170315.25808@idt.unit.no>
Date: 31 Oct 90 17:03:15 GMT
References: <1156@iceman.jcu.oz> <1990Oct30.173846.6928@idt.unit.no> <1990Oct31.012758.26467@jarvis.csri.toronto.edu>
Sender: news@idt.unit.no (Usenet news admin)
Reply-To: daglem@solan5.solan.unit.no (Dag Lem)
Organization: University of Trondheim
Lines: 33

In article <1990Oct31.012758.26467@jarvis.csri.toronto.edu>, leblanc@eecg.toronto.edu (Marcel LeBlanc) writes:
|> 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

No, I have not read BYTE. I have read IEEE Micro (OK so the articles were written by Motorola guys).

|> 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.

Well at least I use the fancy addressing modes of the 680x0 series. Perhaps the c compilers don't, but I cannot agree with you that they are a waste of silicon.

|> 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.

Motorolas claims (OK they are claims) the 68040 on the average uses 1.3 cycles per VERY useful integer instruction. I can't see what makes the number 1.27 seem so much smaller than 1.3 to you :-)

|>Marcel A. LeBlanc  --  Electrical Eng. Computer Group, Univ. of Toronto
|>-----------------------------------------------------------------------
|>leblanc@eecg.toronto.edu		else: uunet!utcsri!eecg!leblanc


    __		      /                       |> Shorter of breath
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