i686 binary executes on i586?

Hi,

I have compiled 'chown' (in fileutils, statically linked and stripped) on an i686 box and tried to run it on i586 box.
I need to understand why
this one fails:

root:/# /bin/chown root:daemon try 
Illegal instruction (core dumped)

but this one succeed:

root:/# /bin/chown root:root try

Also, in general, how can I tell an i686 binary from an i586 binary (or lower). Tool /usr/bin/file does not help much.

Thanks,

-T