For some unknown reason, we stick a -1 in cpu_2_node when we unmap a cpu 
on i386.  We're better off sticking a 0 in there, because at least 0 is 
a valid value if something references it.  -1 is only going to cause 
problems at some point down the line.  Besides, we initialize the array 
with 0's, so undoing it should return it to that same value.

Cheers!

-Matt