Why do I get multiple directories called 'ff' in /proc/bus/pci?

You are probably using a machine which would require PCI domain support from the kernel to correct the display. PCI domain support is not included in the 2.4 kernel shipped in Red Hat Enterprise Linux 3. It is, however, available in Red Hat Enterprise Linux 4. The lack of PCI domain support should not hamper the working order of the machine or of the PCI devices.

Example output from /proc/bus/pci would look similar to the following:

# ls /proc/bus/pci
00  01  02  03  0a  10  11  18  1e  1f  26  2c  2d  34  devices ff ff ff ff ff ff

# ls /proc/bus/pci/ff
02.0  02.1  02.2  02.3  03.0  03.1  03.2  03.3  05.0  05.1  05.2  05.3  05.4  05.5  05.6