If you want to change the resolution your installation set, check your /etc/lilo.conf file. In it, you will find information about the vga variable regarding kernel booting resolutions. In short, all you need to do is change the resolution value code of the vga variable, re-run lilo (i.e. /sbin/lilo), and reboot.
If you would like more information regarding framebuffers, you can check /usr/src/linux/Documentation/fb directory. In it you will find more information about framebuffers.