Modeline creation and assignment is a matter of pure arithmetic and while AdvanceMAME excels at performing such calculations, occasionally it's nice to assume total control and dictate every aspect of a game's display.

From the above picture, we can see how AdvanceMAME divides images into columns and rows. The notation is mathematically intuitive, columns are simply abbreviated as X and a lines are simply abbreviated as Y. While not shown above, "clock" is used to represent the refresh rate. With this information in hand we can quickly make our way through many of AdvanceMAME's display_adjust parameters. But in order to do so, let's return to our problem of displaying a vertical game on a horizontal monitor.

As you'll recall, if we take a vertical game and display it on a horizontally mounted CRT, we run into a bunch of problems. Unless we change the horizontal clock or the vertical clock, several lines are missing. Additionally, unless we adjust the number of columns used by the mode, the image's aspect ratio is incorrect. As shown below.

While before we assumed our theoretical CRT supported multiple horizontal scanning rates, lets now assume it doesn't; that is, that it's a fixed frequency CRT that only supports a scanning speed of 4 seconds/line. If this is true, then, unfortunately, certain sacrifices must be made to display our game. (On traditation arcade monitors, this scenario is the norm. You must often decide between a perfect lossless image out of vertical synchronization or a lossy image in vertical synchronization. As such a decision is based solely on opinion, there is no one best solution.)

Lucky for us, AdvanceMAME understand's our woes and makes it very easy for us to flip through an array of choices and assign our favorite solution. More importantly, we don't have to commit to one generic solution for all our games. We can easily decide to stretch one game, use borders on another, sack the vsync on another, or just axe a few lines.