AGP_I810_GTT
bus_write_4(sc->sc_res[0], AGP_I810_GTT + index * 4, pte);
pte = bus_read_4(sc->sc_res[0], AGP_I810_GTT + index * 4);
AGP_I810_GTT + (i >> AGP_PAGE_SHIFT) * 4, i | 3);