Here is the summery of letters that I have received to my question:

When recompiling the kernel on .99pl5, should the -m486
be used for use in a 386 w/ FPU linux box?

Here are the responses that I received from various people.  Thanks for all 
the help guys!  I received excellent, informative responses from linux users.
I thank all who responded to my question, You'all are great.

Neill Means
means@sage.cc.purdue.edu

P.S. When recomiling the kerel, what does profiling support for the kernel do? 
Is it good/bad? Pros/Cons?


[SUMMERY]:
================================
You probably do not want to compile with the -m486 if you want to get the
most performance out of your kernel.  The -m486 flag does some optimizations
for the 486 (FPU or not doesn't matter; optimizations help on a 486sx as well).
These optimizations are due to the instruction timings and pipeline handling
on the 486.  The 386 will still execute these instructions, but with reduced
performance.

I have a 386/40 w/387/40 myself.  I compared the latest X distribution, which
is compiled with -m486, to the previous one, which is not, and there is
a noticeable decrease in performance.  (this is especially visible when
scroling in an xterm)
-- 
           | Anatoly Ivasyuk @ Rochester Institute of Technology |
           |-----------------------------------------------------|
           | anatoly@nick.csh.rit.edu |  ani0349@cs.rit.edu      |
           | Computer Science House   |  Computer Science Dept.  |
           |-----------------------------------------------------|

================
Theoretically the 486 is capable of going super-scalar (executing more
than one instruction in a clock cycle) for certain combinations of certain
instructions. These combinations are not neccesarily the obviously fastest 
way of generating code to do something. So, the -m486 switch causes the
compiler to generate code that will run a little faster on a 486 and a little
slower on a 386.

You would probably do a bit better to compile with out the switch if you don't
have a 486.
quoted text
>
>Sorry about the ignorance of my question.  
Not a bad question at all. :)

jem.
--
jem@sunsite.unc.edu\/sunSITE admin

==================================================
All -m486 does is cause generated code to be placed so as to improve the
performance of the 486's built-in cache.  On a 386 it wastes a *little* memory
with no speedup... but also no slowdown.

++Brandon
-- 
Brandon S. Allbery                                       bsa@kf8nh.wariat.org

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