Hi msingleton1977,
Arcade_OSD doesn't show the horizontal frequency because that information is not available, the OS doesn't care. However, it's easy to guess it once with some practice.
15/31 are kHz, not Hz. This is horizontal frequency.
1) Is there a way to exclude resolutions in GroovyMame? So, it uses 512x384 instead of 512x448?
You can't exclude resolutions in GroovyMAME. GroovyMAME assumes that if you have a resolution available, it's because it works.
However you can force a given game to run at a different resolution by means of an ini file. But you can't do this globally. And it's a bad solution if you ask me.
2) Is it possible for a damaged monitor to display some resolutions perfectly and others not?
I don't believe that's possible.
3) Maybe the ArcadeVGA is damaged? Would I get a better result by just buying a regular video card and using Calamity’s drivers?
I don't think the AVGA is damaged.
I mean these things are not totally random. There is usually a rule for a group or resolutions that does't work.
Anything below 288 lines is 15 KHz.
512 x 384 is 24 KHz, so that means that range is probably fine.
512 x 448 is either 15 or 31 KHz, depending if interlace is on. Interlace means a shaky picture, but you need to judge if the shake you're seeing is due to interlace or it's something different.
The tri-sync utility however should remove interlaced resolutions and make them progressive, as far as I understand.