PCI_CB_IOLIMIT0
sc->sc_iolimit[0] = pci_conf_read(pc, tag, PCI_CB_IOLIMIT0);
pci_conf_write(pc, tag, PCI_CB_IOLIMIT0, sc->sc_iolimit[0]);
pci_conf_write(pc, tag, PCI_CB_IOLIMIT0, 0);