I don't know if there is a kernel framebuffer driver available for the Geforce 4, or if it's compiled into the kernel used by Amithlon. However, if everything else fail, there is always the VESA support. However, this will not allow you to change resolution from within AmigaOS, you have to make the change elsewhere. That is, install Amithlon on a harddrive and follow the docs on the Amithlon homepage on how to change the VESA resolution and colordepth.