​Back in the days of CRT TV's the visible image was cropped, with some of what was called 'over scan' wrapped around the edges of the CRT picture tube. When computer monitors got cheaper, more people starting using them instead of their TV's. The side effect of this transition resulted in less of the over scan image being chopped off. And this trend continued with the advent of modern HDTV's, which now display every bit of possible video coming out of the A8. As a result, some games and applications that take advantage of this normally 'hidden' area of the screen to hide various graphics manipulations (akin to racing the beam), now have every bit of these artifacts revealed. So the main idea behind the GTIA V-Gate board is to hide these areas that were never meant to be seen, by 'blacking' them out.