15" AlBook 896x600 Framebuffer Mode?

[ms419]

I want to set the console resolution on my 15" AlBook to 896x600, but I 
can't find the requisite framebuffer mode.

The console is currently set as follows:
        fis:~# fbset

        mode "1280x854-60"
            # D: 79.815 MHz, H: 51.963 kHz, V: 60.003 Hz
            geometry 1280 854 1280 854 32
            timings 12529 128 16 8 1 112 3
            rgba 8/16,8/8,8/0,0/0
        endmode

        fis:~#

I've poured over the fbset & fb.modes manpages. Anyone know, or know 
how to get, the framebuffer mode for 896x600 (or 720x480, 1152x768) on 
a 15" AlBook?

Thanks!

Jack