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: <1990Oct31.165728.3196@jarvis.csri.toronto.edu>
Keywords: A RISC Mac?  So what?
References: <1156@iceman.jcu.oz> <1990Oct30.173846.6928@idt.unit.no> <1990Oct31.012758.26467@jarvis.csri.toronto.edu> <1990Oct31.170315.25808@idt.unit.no>
Date: 31 Oct 90 21:57:28 GMT
Lines: 47

daglem@solan5.solan.unit.no (Dag Lem) writes:
>|> 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 :-)

That's the point I was trying to make - the clocks/instr are nearly
identical if you can trust Motorola's claims.  You made the statement that
RISCs "do virtually nothing with one instruction", when it is clear from
MEASURED data that the R3000 does MORE with it's instuctions than the yet to
be measured 68040.  At identical clock speeds, the 68040 _might_ come close
to the R3000 in performance, but then the R3000 is already up to 40MHz,
while the 68040's best is 25MHz.

Another thing to note is that based on published performance claims,
Motorola's statements of VAX-MIPS are not nearly as trustworthy as MIPS'.
Here are a few numbers comparing measured SPEC data vs. Published MIPS:
(these numbers were compiled by John Mashey)

SPEC	SPEC 	SPEC	Published	System
Integer	Float	mark	mips
14.6	10.8	12.2	17.0		Motorola 8864SP, 20MHz, 128K
18.3	13.5	15.2	21.0		Motorola 8864SP, 25MHz, 128K
21.4	15.8	17.8	25.0		Motorola 8612, 33MHz, 32K

19.4	16.8	17.8	20.0		MIPS Magnum, 25MHz, 64K

Motorola's idea of MIPS is not as inflated as other companies, but you do
have to take their claims with a grain of salt.

>    __		      /                       |> 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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