🚀 go-pugleaf

Can someone help me with a puzzling problem?

In my current C programming project, I have written some functions that
perform statistical things on 400 separate data sets (linear regressions,
standard errors, etc).  This number-crunching part takes about a minute to
complete when I run it on my Amiga.  My Amiga uses a 68000 running at 14 MHz
(twice the normal cpu speed) and no math chip.  The compiler is Lattice C
4.0 in 32-bit addressing mode (similar to the IBM "large" memory model).

Naturally, I wanted more speed, so I ported the program to an AT&T 386WGS
at work, which is a 25 MHz 80386 IBM compatible.  I compiled it using
Turbo C 2.0, large memory model.  Then I watched in chagrined disbelief as
that number-crunching section still took about a minute to execute --
actually a few seconds longer than my Amiga.  All source code was the same!

This is plainly ridiculous, I thought.  I was always under the impression
that there is NO WAY a 14 MHz Amiga can match the performance of a 25 MHz
80386 machine.  I thought of a few possible reasons.  I am sure they are
way off base, because I have little familiarity with IBM-style architecture,
but here they are:

1)  Perhaps MS-DOS takes up a lot more overhead than AmigaDOS, but I doubt
    it.  I always considered MS-DOS to be an operating system that gets in
    the way of the task at hand only minimally.  I had no other programs
    resident.  If anything, the Amiga Exec had more overhead, since there
    were two other "active" background tasks and 16 "waiting" background
    tasks for the operating system to worry about.

2)  Possibly the IBM display is CPU-bound, as in the Macintosh, where
    program execution is only performed during vertical screen blanks.  This
    isn't the case, is it?  Isn't the video circuitry independent of the CPU?

3)  Maybe the Turbo C compiler for IBM compatibles is not as efficient as
    the old Lattice compiler I use for the Amiga.  I find it hard to believe.
    Perhaps each compiler's implementation of math functions like sqrt()
    are different enough to account for this incident.  The math library I
    used on each machine was the default.  On the Amiga, this is the slowest
    library.  There are others (IEEE, FFP, etc) which are faster but they
    sacrifice precision.

4)  Might the 68000's math instructions be more streamlined than those on the
    80386?  It takes 70 clock cycles to do a multiply and 158 to do a divide
    on a 68000, plus at most 16 cycles to calculate addresses.  I don't know
    what the specs are for an 80386.

5)  I know the 80386 has special modes of operation, incompatible with
    previous chips, that allow it to run at its full potential.  Is this
    the reason my program isn't running at its rightful speed?  Are these
    special modes accessible when using DOS?  If so, how?

I have absolutely no intention of starting a computer war here.  This is
new to me, and seems bizarre.  I would like an explanation, and if possible
some suggestions on speeding up the execution of my software on the 80386.
IBM compatibles are the target machines for my software anyway (I just like
doing the development on the Amiga).  Please e-mail me any help (or flames?)
and I'll summarize.

-- 
     ///  Alex Matulich
    ///  Unicorn Research Corp, 4621 N Landmark Dr, Orlando, FL 32817
\\\///  alex@bilver.UUCP    ...uunet!tarpit!bilver!alex
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