To change your sun's resolution, use the program m64config. It has a good man file.
m64config -prconf shows your current settings and the other available modes. It doesn't necessarily know about your monitor's available modes.
To set your computer's resolution the way mine is set, type this string:
m64config -depth 24 -res 1152x864x75 now
(the "now" part of this means change it immediately.)
This is the highest resolution that works with reasonable color depth and
high refresh rate.
When you do this, the resolution will change and everything will be scrambled. Reboot the machine by pressing the power button next to the cd drive then pressing enter. On reboot everything should work.
Note: If you'd prefer to have a little higher resolution at the expense
of refresh rate, use the following string in place of the one above:
m64config -depth 24 -res 1152x900x66 now