Anyone knows how the I/O ports of the primary/secondary controller acts on a i430fx PIIX?

I see that the BIOS has written some weird values to the PCI BAR registers, which seems to imply there's some unknown protocol going on (BAR0=170h, BAR1=370h, BAR2&3 are in the FFxx range), or sometimes even weirder addresses appear, depending on the BIOS settings?