GFFB_DISPLAYSTART
GFFB_READ_4(GFFB_CRTC0 + GFFB_DISPLAYSTART),
GFFB_READ_4(GFFB_CRTC1 + GFFB_DISPLAYSTART));
GFFB_WRITE_4(GFFB_CRTC0 + GFFB_DISPLAYSTART, sc->sc_fboffset);
GFFB_WRITE_4(GFFB_CRTC1 + GFFB_DISPLAYSTART, sc->sc_fboffset);