change resolution of text mode in ubuntu 8.04

Boot ubuntu 8.04 from text mode:

Change,

/etc/X11/default-display-manager

#/usr/sbin/gdm
false

Then, change resolution of text mode

add 'gva=773' after 'ro' in grub configure file

     640x480 800x600 1024x768 1280x1024
8bit  769    771     773      775
15bit 784    787     790      793
16bit 785    788     791      794
24bit 786    789     792      795