software written elsewhere in the world?
The 50Hz vertical refresh frequency of PAL machines translates into more vertical blank interrupt (VBI) time for demos and other computation-intensive graphics software, when compared to the time available for VBIs on NTSC machines with the faster 60Hz refresh frequency. So PAL demos and games that won’t work on NTSC machines are usually returning from a VBI too late. Some also attempt to use more vertical resolution (“longer” display lists) than an NTSC display can handle. Note that the reverse is also true. Software using VBIs will run more slowly on a PAL Atari than on an NTSC Atari. Replacing the NTSC ANTIC chip in an NTSC Atari with a PAL ANTIC changes the screen refresh rate to 50Hz, allowing most of the PAL-only European software to run on a North American NTSC Atari. However, make sure your display device can support a 50Hz PAL signal first! North American Atari users can also obtain and use real European PAL Atari machines, with the same caveat concerning the display device. B
