KM266 Video Linux
It took a bit of googling to find this easy fix to getting KM266 video working in X. Specifically with Debian (Sarge) but probably many other distro's.
all you need to do is to make sure that you specify
using the VESA driver before installation. Then after installation,
edit the XF86config file, by changing the driver from "vesa" to
"savage", and adding an option: "useBIOS" "no".
Source: http://lists.hosef.org/pipermail/luau/2003-September/014125.html