i have this mazellan 500a for a year. it’s an old monitor, even the color had blurred when i bought it in a used market. i use it in my ubuntu 6.10 edgy etch cpu. the xorg works fine, it could enter the gdm. but the resolution stay in 600×480.
then i took a look to /etc/X11/xorg.conf i found out the monitor section is like these
after finding out in www.computechgroup.com i realized that the configuration missing something. the HorizSync and VertRefresh. So i added the command into it.
then restarting the ubuntu and the resolution worked well into 1024×768