From: franklin@elfie.async.vt.edu (John Franklin)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: Intel HW
Date: 9 Apr 92 09:33:40 GMT
Reply-To: franklin@elfieasync.vt.edu (John Franklin)
Organization: Elfie

>jbono@tension.UUCP (John Bono) writes:
>
>>2.  The 486 is *significantly* slower than the '040, *particularly* at
>>floating point math.  This is due to the fact that the 486 has significant
>>ties back to the 8088(note--I said 8088, *not* 8086).  The 8088 is an 8-bit
>>chip.  This means that the 486 has to be run 8088 code.  In thirty two bit
>>applications, the 040 is significantly faster because it need not worry about
>>running 68K code, since the 68K had a 32-bit internal instruction set(like the
>>386sx).  In addition, the '040 has a method of pipelining instructions which

To wit, in article <1992Apr9.060532.24892@ux1.cso.uiuc.edu> 
nap42487@uxa.cso.uiuc.edu (Nishith A. Patel) responds:

>First, how can you call the 8088 an 8-bit chip while calling the 68000 a
>32-bit (or implying it with the refernce to 32-bit instruction set). The
>8088 is a 16-bit chip wih a 8 bit external bus, just like the 68000 is
>a 32 bit with 16-bit external bus. 

A valid point.  The bus/instruction bit size should be specified, and 
not interchanged.  (Apples==Oranges) logic is not valid.

>second, this is not nearly enough eveidence to claim that the motorola line
>is faster, if you look at the instruction sets of the two, you will see
>the Motorola chip is in a very sorry state.

Is it?  In what way is it in a very sorry state?  I'm rather familiar
with the Motorola chips instruction set (both the 65XXX series and the
68XXX series) and have not been left wanting on either of them.  The
65XXX series is one-address instruction class chip, the 68XXX is a two- 
address instruction class chip, and I believe that the 80XXX is a three- 
address instruction class chip.  I'm unaware of how much you know about 
microprocessor architecture, so I'll explain what one/two/three-address
instruction class chips are.

A one-address instruction chip will have instructions with one address
listed in the instruction.  The other address is an implied register
(typically called an accumulator).  The instruction:

	add x

would add the value in register x to the current value in the accumulator
and store it in the accumulator.  Similarly, a two-address instruction 
chip will have two address listed with the first one being the target
address.  That is, the instruction:

	add d0,d1

would add the value in register d1 to the current value in register d0 
and store it in register d0.  A three-address instruction chip will
list a destination that is independent of the operands.  So,

	add d0,d1,d2

will add d1 and d2 and store it in d3.  Having a higher address instruction
chip does not automatically make it more powerful.  The higher address
instruction chips tend to have shorter programs, but any one individual 
instrction will take more space than on a lower address instruction chip
and take more cycles to execute.  It's a trade-off.  Lower chips tend
to be a bit more more effecient in overall speed, but at the cost
of longer programs.  Would you care for an example?

Back to the point at hand, the sorry <??> state of the 68XXX instruction
set.  With the above in mind, could you tell me why the 68XXX is in a
sorry state?  What is the 68XXX lacking?

[John Bono says:]
>>further amplified since the Amiga has very little OS overhead.  Actions that
>>suck CPU time out of traditional computers like the PC and MAC are covered by
>>the Amiga's custom chips, such as screen refresh, disk access, etc.  This is
>>why most Amigas will consistently outperform systems with much more powerful
>>CPUs, i.e. an A3000-16 will consistently outperform a Mac IIci, though the
>>IIci has a more powerful CPU, and in most cases, an A3000 will outperform most
>>486's or IIfx's under heavy multitasking, for the same reason.

[Nishith A. Patel responds:]
>Screen refreshes! you have to be joking! If the Amiga becomes a powerful
>machine when doing a trivial chore like screen refreshes (compared to the
>utility and ability of doing anything else a computer does), then it
>obviously sucks when doing some serious work. Nobody takes screen
>refresh into account when considering how powerful a computer is. As for

Trivial?  Indeed not, sir.  Take two text decompression programs.  One that
writes the output only to disk and another that print it out as it
decompresses it as well as writes it to disk.  If this were a trivial 
thing, then the difference in execution times should also be trivial.
However, it's not even close (even on a mainframe where I've seen this 
done).  The one that does the extra output is far slower than then one 
that does no extra output.  In a system like the Mac or the Amiga where
all the output is graphical in nature, and comparing it to a comparable
setup on an MS-DOS machine (eg, Windows) where the x86 has to do all
the screen updates itself, then the extra chips do make a great deal of
difference.  Scads.  Screen refreshes are very important as they take
a great deal of time to do.

Also, in this day and age, multimedia and easy user interfaces are the
big rage.  A character based system has a hard time cutting it against
a graphics based system.  Any system designed on a character machine
can be done on a graphics machine.  However, the converse is not true.
Character based machines are faster at what they do than the graphics
based machine is at doing the EXACT SAME THING.  It's just that
the graphics based machine can do quite a bit more than character based.
Character based machines try to do the same but just really
can't get the resolution or smoothness (as well as the flexabilty of
icons and other graphics) that graphics based machine do.

Serious work?  Please define.  If you're meaning things like calculating
fractals or doing other massive number crunching, then you're right,
screen refreshes are generally not taken into account.  But then,
you're generally looking for a supercomputer or similar machine.
At the very least a machine with a math co-processor.

Obviously sucks?  You have a leap of logic that I'm not following.
The fact that a machine can redraw the screen very quickly doesn't make
it a bad number crunching machine.

[Nishith A. Patel continues:]
>disk access, the same applies. The Amiga chipset only provides support for
>floppy drives, not hard drives. The floppy drive speed is of no concern
>to people doing any real work with a computer. You use a hard drive, not
>a floppy. Unless the chipset is real magical and makes the floppy drive
>faster than a hard drive and allows more megabytes and megabytes of storage
>on a flopp,y which obviously is not the case, good floppy access doesn't
>do squat for the power of the system. 

In as much as an Amiga can be (and in may cases is) run entirely off of
floppies, this does become quite an issue.  Again, your use of "real
work" disturbs me.  Floppy access isn't a major concern for IBM users.
However, that's mainly because few programs are small enough to fit on a
floppy or even two.  OTOH, the only Amiga program that I can think of
that requires a hard drive is Amiga UNIX.

jf
--
John Franklin	(aka 'jf')
franklin@elfie.async.vt.edu
franklin@csugrad.cs.vt.edu
Newsgroups: comp.sys.amiga.advocacy