If you run on 4x0/6x0 model Towers, beware of this:
The default maximum virtual address space of a process is 1Mb.  This is
not enough to run gcc -O on large files.  The problem is typically seen
while compiling gcc with itself.  You have to change your kernel
configuration file, adding a line like this:
MAXUMEM = 4096
Then relink the kernel and reboot.
