32-bit ABI.  Most modern machines are likely to require this.
This is no longer needed for GC7 and later.
</dl>
<H2>Additional requirements for a basic port</h2>
In some cases, you may have to add additional platform-specific code
to other files.  A likely candidate is the implementation of
<TT>GC_with_callee_saves_pushed</tt> in </tt>mach_dep.c</tt>.
This ensure that register contents that the collector must trace
from are copied to the stack.  Typically this can be done portably,
but on some platforms it 