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From: daveh@cbmvax.cbm.UUCP (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: Re: Amiga vs. IBM-PC: A Performance Query
Message-ID: <1913@cbmvax.cbmvax.cbm.UUCP>
Date: Thu, 21-May-87 12:03:15 EDT
Article-I.D.: cbmvax.1913
Posted: Thu May 21 12:03:15 1987
Date-Received: Sat, 23-May-87 12:22:03 EDT
References: <127@belfry.sandiego.NCR.COM>
Distribution: world
Organization: Commodore Technology, West Chester, PA
Lines: 56

in article <127@belfry.sandiego.NCR.COM>, geoffk@belfry.sandiego.NCR.COM (Geoffrey Kim) says:
> Keywords: Amiga, IBM, comparison
> 
> Having been a previous PeeCee owner (pitiful, aren't I?)  I
> was just curious how the Amiga rates in terms of performance?
> Concern here is that Lattice compile/execution times will be
> N times slower/faster than running it on a PC?  What would
> be the PC equivalent of the Amiga's 68000 @8Mhz?  Would it be
> a (an?) 8088 @6/8Mhz or a 80286 @6/8/10/12Mhz or ?
> 
> Anyone?

How 'bout me?  From a straight hardware point of view, a 68000 running
at 8MHz is probably closest to an 80286 running at 8MHz (without too much
knowledge of the '286 specifics on my part).  Both processors have 16 bit
address busses, both take 4 cycles to access memory, etc.  The Amiga's
processor is actually running at 7.16MHz, so it will be a bit slower than
the 8MHz processor.

Looking closer at the architecture, you find that the 68000 is internally
a 32 bit machine in many respects, having 32 bit registers and many 32 bit
instructions.  It has a logical address space of 32 bits, with a linear 
physical address space of 24 bits.  As I recall, the chip has 3 16 bit ALUs, 
a pair will do the 32 bit stuff.  The 80286 is internally a 16 bit machine, 
with an extended segmented architecture and emulation of the original 8088
segmentation.  It also has a 24 bit address space, though of course not a
linear space.  I believe the 68000 has some more powerful instructions,
but the '286 benefits from smaller instruction lengths and the efficiency
that its 64K segments give you on smaller programs (though, via PC relative
coding, the 68000 can also act more efficiently on small programs).

Anyway, what this means is that 68000 programs are usually longer for the
same operation than 80286 programs.  If you're dealing with operations of
less than 64K in length, the 80286 stuff may run faster than an equivalent
68000.  The 80286, however, takes a small performance hit when running
programs larger than 64K, and a big performance hit when manipulating 
data objects greater than 64K in size.  The 68000 has no problem with these.
Also, most current 80286 systems are running in 8088 emulation mode, which
is another big performance hit.  Because of this, the Amiga will sometimes
run up to 3x the speed of an AT on CPU bound tasks.

Finally, the Amiga has a few devices designed to offload work from the 68000.
The Bimmer (Blitter) is a device optimized for graphic maniplulation that
moves images (with barrel shifting), draws lines, and fills areas faster
than the 68000 could.  The Copper (co-processor) is a tiny processor that
accepts 3 types of commands used for altering graphic configurations.  A
few other items, too, make the Amiga's overall performance in its graphic
environment usually exceed that of similar machines.

> Thanks in advance.  Geoff K.
> 
>  
-- 
Dave Haynie     Commodore-Amiga    Usenet: {ihnp4|caip|rutgers}!cbmvax!daveh
"The A2000 Guy"                    BIX   : hazy
	"These are the days of miracle and wonder" -P. Simon