That old patch: http://www.clustermatic.org/pipermail/linuxbios/2003-July/004046.html was the first one I put up, there have been a lot of fixes since then.
Go to this site: http://www.xdr.com/dash/linuxbios/ get this patch: http://www.xdr.com/dash/linuxbios/freebios-nxtv-patch-20030705.gz
That is more complete.
The slow video rendering might be related to the int21 handlers in mainboard.c. I found performance wasn't as good as under award bios until I fixed that. It looks like the patch you applied doesn't even handle the bios callbacks the VGA bios is expecting.
-Dave