Some time back, a change was made (by Greg Troxel, I thought) so that
rbus was calculated automatically.  It doesn't seem to happen on
amd64.  I have 3GB machine; here's what happened:

cbb0 at pci6 dev 0 function 0: Ricoh 5C476 PCI-CardBus bridge (rev.
0xba) cbb0: can't map socket base address 0xf8300000
cbb0: can't map socket base address 0xffffffff80d02810: io mode
cbb0: WARNING: power management not supported
cbb0: bad Vcc request. sock_ctrl 0xffffff88, sock_status 0xffffffff
cbb0: disabling socket
cbb0: interrupting at ioapic0 pin 16 (irq 10)
cbb0: WARNING: powerhook_establish is deprecated
cardslot0 at cbb0 slot 0 flags 0



		--Steve Bellovin, http://www.cs.columbia.edu/~smb