S3/Trio64 video board only showing 256 colors

I have a Diamond Stealth 64 DRAM 2 MB PCI video board. It is detected by RedHat as Trio64 and by windows 98 as S3/Trio 64.
It supports 1024 x 768 16bit color @ 75Hz.
Knoppix 3.3 give me a kernel panic when it started the X server.
Knoppix 3.4 boots ok, but in 1024x768 8 bit color. Is there any way I can change that? KDE looks awful in 256 colors.

I think the normal VESA driver will be fine.

kxconfig

It hangs when I try to save the changes. I can't answer the confirmation dialog box.

Try it in console login.