PCI mapping on large memory 32-bit machines

[Timothy Miller]

On x86 with PAE and 4 gigs of RAM or more, where do memory-mapped I/O 
devices get mapped (in the physical address space)?  Most PCI devices 
can't handle 64-bit addresses.  Can PC chipsets physically remap some of 
the RAM to above 4 gig?  Or do you just lose that much RAM?  If both RAM 
and some I/O device are mapped to the same location, isn't there a conflict?