The jumpers are pretty well labeled and described on the board. You can jump the speed of the RAM (60ns or 70ns I believe) And the other jumper lets you cache the ROM data to RAM for theoretically better performance but you loose 512kb. That's about it...
To disable on start-up hold down the "2" key. To re-enable hold down the Ctrl-A-A (reboot) keys for more then 10 seconds. (It's also re-enabled after powering off the system)
