Why do some PAL games have black borders?
If a game is developed using a PAL system, then all 625 lines are used on the screen. Hence, no black borders. However, most games are developed in Japan and the US using only 525 lines, leaving 100 lines redundant. These show as ugly black borders on the top and bottom of your screen and runs approximately sixteen percent slower. Fortunately European developers discovered that by using polygons the image could be slightly stretched and by developing a PAL version alongside the NTSC game allowed easier conversions. Because of the growing size of the PAL market Sony now expect the best possible conversions before granting a license.
