Compiling for i686

[David Vos]

I have an Athlon from which I need to get full performance.  I was trying
to edit the specs file so that all compilations will be for the i686.  I
thought I set the default cpu properly, but I don't know if I did so
correctly.

How can I set gcc to always compile as if I set the '-march=i686
-mcpu=i686' parameters?

How can I test to see if it is actually doing this?

I tried:
gcc test.c -o testd
gcc test.c -o test3 -march=i386 -mcpu=i386
gcc test.c -o test6 -march=i686 -mcpu=i686

According to cmp, testd and test3 were exactly the same, while testd and
test6 were different.  This leads me to belive that the compiler is
assuming i386.  Is there a better way to check this?  Or is there a web
page somewhere that describes how to do this?

(This is for a Beowulf cluster on which I will be running intensive
programs all summer.  I need to sqeaze everything I can out of it).


David