 This technique can achieve an absolute maximum of 704 pixels horizontally in 25 MHz mode and 792 at 28 MHz without altering the actual sync width (in real-world cases, e.g.with 800 pixel wide mode, the sync pulse would be shortened and a small porch area left in place to prevent obvious visual artefacting), and as much as 523 or 447 lines at the standard 60 and 70 Hz refresh rates (again, it is usually necessary to leave SOME porch lines intact, hence the usual maximum of 410 or 512 lines at these rates, and the 50 Hz maximum being 600 lines rather than 626).Conveniently, the practical limits of these techniques are not "quite" high enough to overflow the available memory capacity of typical 256 KB cards (800×600 consuming 235 KB, and even the theoretical 832×624 requiring "only" 254 KB), so the only concerns remain those of monitor compatibility.