 All derived VGA timings (i.e.those which still use the master 25.175 and 28.322 MHz crystals and, to a lesser extent, the nominal 31.469 kHz line rate) can be varied widely by software that bypasses the VGA firmware interface and communicates directly with the VGA hardware, as many MS-DOS based games did.However, only the standard modes, or modes that at least use almost exactly the same H-sync and V-sync timings as one of the standard modes, can be expected to work with the original late-1980s and early-1990s VGA monitors.