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From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: 68040 (Was Re: Amiga 3000)
Message-ID: <10216@cbmvax.commodore.com>
Date: 16 Mar 90 16:56:02 GMT
References: <13479@baldrick.udel.EDU> <9884@batcomputer.tn.cornell.edu> <100578@convex.convex.com> <5812@tekig5.PEN.TEK.COM>
Reply-To: daveh@cbmvax (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 75

In article <5812@tekig5.PEN.TEK.COM> wayneck@tekig5.PEN.TEK.COM (Wayne C Knapp) writes:
>In article <100578@convex.convex.com>, swarren@convex.com (Steve Warren) writes:
>> In article <6398@sbcs.sunysb.edu> root@sbcs.sunysb.edu (Systems Staff) writes:
>> >In article <3951@nmtsun.nmt.edu> dksnsr@nmtsun.nmt.edu (Dr. Mosh) writes:
>>                                     [...]
>> >>...based on pure processing performance, the 68040 IS Faster...

>All of this talk about a 68040 being faster than anything isn't worth 
>anything until one can get a 68040 in a real system.  

However, there is one thing you can be certain about -- the 68040 will run
your Amiga programs faster than any SPARC machine.  And it'll certainly give
any existing RISC machine a run for its money.  

For those who don't know much about the 68040, I can supply a few interesting
details.  It actually looks a bit like an 88k system, only on a single chip.
Like the 88k, the 68040 has separate MMUs for the instruction and data paths,
and large physical caches (4k each, vs. the 16k each of the 88k).  However,
cache hits happen as quickly as register accesses.  This is extremely 
important for any older architecture trying to achieve the speed of the newer
architectures.  While the question of how many registers are needed is far
from settled, most new architectures pick from 32 (MIPS and 88k) to zillions
(SPARC and 29K).  The 680x0 architecture guessed better than the 80x86, but
it's still a bit short.  But with cache access time the same as register
access time, the need for more registers is greatly reduced, while at the
same time maintaining compatibility.  Another neat trick the 68040 uses is
in its clocking.  The 25MHz clock governs bus events, and in that sense a
25MHz 68040 exhibits external behavior similar to other 25MHz machines.  But
ALU and other internal events are governed by a 50MHz clock, allowing many
internal things to happen much faster than they would in a traditional 25MHz
CPU.

Of course, just like the techniques used in RISC chips like the 88k were
adopted and in some cases improved for the 68040, the next generation of
RISC chips may be able to adopt some of the 68040's ideas, or others that
have been explored since then.  Another thing to consider, especially in
the case of SPARC, is that no one's yet introduced a SPARC processor built
with the same level of technology as the 68040.  Sun's original version was
built in a standard commercially available gate array, while the 68040's
process is state-of-the-art 0.8 micron CMOS.  So even if the 68040 now does
"things" faster than some existing RISC CPUs, you'll eventually see RISCs
out with on-chip floating point and cache that will very likely leapfrog
the 68040.

>So far it is just a bunch of talk.  The 68040 is just being sampled now.  

Sure is...

>There is no way the a company like Commodore is going to be able to get a 
>68040 based computer out this year.  

Remember, sports fans, who said it first.

>When the 68040 is out in systems, it will make some sence to talk about
>its speed compared to a sparc or 88K or whatever.  However until there are
>some real 68040 systems out it isn't really possible to compare performance. 

That's true.  And until Motorola's shipping them in volume, rather than
sampling, you probably won't be able to buy a 68040 system at all.  Most
680x0 companies have known about the 68040, and how to build 68040 system,
for quite awhile.  So, like we saw last year with the 80486, as soon as
production quantities are available, you'll see a number of systems become
magically and instantly available (well, maybe YOU won't see them -- a 
good deal of 680x0 parts go into VME and other industrial computers, while
80x86s are mainly visible in PClones.  You all know the PC/Workstation
folks involved in 680x0 family systems: Amiga, Apple, Atari, Apollo/HP, 
NeXT, NCR, Sony...)

>                                                     Wayne Knapp


-- 
Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests"
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                    Too much of everything is just enough