IMC_GIO64ARB
reg = bus_space_read_4(isc.iot, isc.ioh, IMC_GIO64ARB);
bus_space_write_4(isc.iot, isc.ioh, IMC_GIO64ARB, reg);
reg = bus_space_read_4(isc.iot, isc.ioh, IMC_GIO64ARB);
bus_space_write_4(isc.iot, isc.ioh, IMC_GIO64ARB, reg);