wpcmame...I believe I asked around before without a definitive answer: So games like tapper and tron were interlaced right? If so did the originals have a flicker to the screen that can be common when interlaced?
Yes, popeye and tapper used interlaced displays but they don't flicker. Interlace only means that you draw odd lines on one frame and even lines on the next. If both lines contain (almost) the same thing it will look like a non-interlaced display.
Game designers used lot of tricks to avoid flicker (low contrast on non-moving objects, don't use thin horizontal lines etc). Sometimes you can use the flicker to your advantage. In popeye, the cans and thing that you knock down on bluto (bee-nest?) flickers but that only makes them easier to see.
Modern PS2 and XBOX games on your TV also uses interlaced display but you hardly notices the flicker (mostly due to a lot of moving objects and good antialiasing algorithms that remove sharp edges).
For some strange reason my graphic card (SiS6326) refuses to show resolutions below 300 lines properly so I always use double sized (i.e. interlaced) displays for all games with less than 300 lines. Advancemame automatically doubles the pixels both horizontally and vertically so the there is no difference in the displayed picture.
Unfortunatly MAME has messed up the interlaced games. Popeye is marked as 60Hz while Tapper is marked as 30Hz (or the other way around) so to find interlaced games in mame you have to look for games with more than 400 lines. Some recent games probably used 31KHz monitors so you have to exclude them.