From: mykes@amiga0.SF-Bay.ORG (Mike Schwartz)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: 040 and 486_ (bunch O' Kaka anyway)
Distribution: world
X-NewsSoftware: Amiga GRn V1.29 4/10/92 (Beta) by Mike Schwartz
Date: 15 Apr 92 11:59:12 PST
Organization: Amiga makes it possible

In article <1992Apr15.003149.29648@ux1.cso.uiuc.edu> nap42487@uxa.cso.uiuc.edu (Nishith A. Patel) writes:
>mykes@amiga0.SF-Bay.ORG (Mike Schwartz) writes:
>
>
>>The way to do the benchmarks is to code them in hand crafted assembly.  That
>>way, the quality of the 'C' compiler does NOT come into play.  The same coder
>>should do both programs.
>
>>The above test will show how the shuffling of registers makes a difference.
>
>If they are in assembly language, we have to use two programmers. One who
>specializes in the 68k line, and one who specializes in the 486 line. If
>we used one programmer, which one would he develop better code for, the
>one he is better at or the one he is worse at? 

This is a fallacy in your thinking.  Anyone who knows assembly for any machine
can do the benchmark coding.  If you know assembly language, you know assembly
language.  You may have to refer to the 80486 or 68040 manual to choose the
most optimal instructions.  I maintain that the assembly coder will do 
equally well on both CPUs.

However, to make you happy, Intel and Motorola have had their own engineers
optimize the benchmarks and the 040 wins every time.  And that's Intel
experts vs. Motorola experts.  Both coding to optimize cache hits, etc.

>Or, use the same compiler, exactly the same. All options should be the same.

If you use EXACTLY the same compiler, you are going to get code for one of
the two cpus.  Code generators have to be different (thus making the compilers
not exactly the same) for different CPU families.  Which compiler would you
prefer to use?  The one that Intel masochists have spent 1,000,000 hours working
on the code generator or the one that Motorola guys have spent 1,000?

>I just checked comp.benchmarks, and someone listed a bunch of machines
>for a test. And machines with the same things, same type of computer, same
>CPU/FPU, same operating speed, same compiler, only different compiler options.
>And the results varied tremendously. (or maybe the options were supposed to
>make a difference, like compiling more or less code or something, I do not
>know. I did not look at the thing closely).

Even GNU will have different code generators for the two cpus.

>Obviously, we are not going to be able to create something fair easily, and
>get some programmers to write a series of tests (just CPU tests, not I/O,
>as I said before) and do it equally, like same proficiency for both machines,
>have all tests listed and not "screened," etc. So we should just find
>something in a Unix magazine or something like that. 

There is validity to other classes of benchmarks, like those you'd find in
a unix magazine.  You want to know, for example, if the 'C' compiler does
a better job for a particular brand of CPU.


--
Author of Amiga GRn, MailMinder, Budokan, Beyond Dark Castle, Dark Castle,
and Genesis Dick Tracy and Marble Madness.
Mike Schwartz  (ames!zorch!amiga0!mykes or mykes@amiga0.sf-bay.org)
1124 Fremont Ave.
Los Altos, CA 94024