Thanks for the link, I've already saw it but I don't know enough linux to understand it...

but if you didn't get it working I think I better shouldn't even try

Yep, in windows is pretty straight forward, just "screen \\.\display2".
It's a pitty becouse GA seems to work with mobility radeon, apart from the second display mame issue, as non mame is working.
Problem is that I cannot get the display name in linux, using groovymame -verbose gives non readable info, something like "found connector '##############'", and those # are square ascii characteres.
I should use "groovymame -connector DISPLAY_NAME" and in mame.ini edit "screen DISPLAY_NAME"?
I guess I'll have to wait for new Groovymame and GA versions...
