Thanks for your words rock145,
I wanna to know if it's possible in groovymame to change the resolution of a cga game to ega resolution? like mortal kombat 399 x 253 to 320x240 24khz
Well you can definitely force a game to run in "EGA" resolution, by setting, for instance: "-resolution 512x384@60". This will work if you're using magic resolutions, however the result will be too bad (stretched).