VGA_CRTC_V_SYNC_START
vga_wcrt(regbase, VGA_CRTC_V_SYNC_START, vsyncstart & 0xff);
par->crtc[VGA_CRTC_V_SYNC_START] = yres + lower - 1;
reg.crt[VGA_CRTC_V_SYNC_START] = vs;
write3X4(par, VGA_CRTC_V_SYNC_START, vsyncstart & 0xFF);
par->crtc[VGA_CRTC_V_SYNC_START] = pos & 0xFF;
vga_io_wcrt(VGA_CRTC_V_SYNC_START, 0xff);