graphics modes. The ANTIC chip uses a Display List and other settings to create these modes. Any graphics mode in the default GTIA color interpretation can be freely mixed without CPU intervention by changing instructions in the Display List. The ANTIC screen geometry is not fixed. A hardware register can direct ANTIC to display narrow playfield (128 color clocks/256 hi-res pixels wide), normal width playfield (160 color clocks/320 hi-res pixels wide), and wide, overscan playfield (192 color clocks/384 hi-res pixels wide). While the Operating System's default height for graphics modes is 192 scan lines Antic can display vertical overscan up to 240 TV scan lines tall by creating a custom Display List. Mode F produces colors through NTSC artifacting and works in a similar manner to the Apple II's graphics modes. The pixel resolution is 320 across but the color resolution half that, thus each group of two pixels will "blend" together to form a single color and four artifact colors may be generated this way. They will be tinted if the foreground and background color are set to something other than black/white/gray. The exact colors produced this way vary with different Atari 8-bit models and also between the CTIA and GTIA chips, thus undesirable artifact colors may result from running software that uses Mode F on a machine other than the one it was developed for. It was not possible to obtain artifact coloring on PAL machines and Mode F will be monochrome on them. Mode F was not widely used by software due to its high memory requirements (8k) and inconsistent artifact colors that did not appear the same on every model of Atari 8-bit computer. Games that utilize it include Sierra graphical adventures such as Troll's Tale and Wizard and the Princess, Lode Runner, and the Ultima series. The video display system was designed with careful consideration of NTSC display methods and limitations. The system CPU clock and video hardware are synchronized to one-half the NTSC clock frequency. Consequently, the pixel output of all display modes is based on the size of the NTSC color clock which is the minimum time needed to guarantee correct and consistent color regardless of the pixel's horizontal location on the screen. The result is accurate pixel size and coloring that does not display color "strobing" defects when horizontally scrolled. (Color strobing is unsightly hue changes in pixels based on horizontal position