I successfully updated the firmware to v6.1 but my problem was mainly a internal gfx-card vs. external gfx-card issue. I removed the FX2-card and successfully installed a woody system (dist-upgraded to Sarge afterwards).
Now I want to ask if it's possible to use a 16bit graphics mode using the builtin gfx-card (I only got 8bit to work). That would be enough for a basic desktop. Or would it be possible to use a "normal" PCI-card for graphics? On parisc-linux.org I saw that Matrox and Voodoo-Cards are supported - I have some Matrox Millenium II and Voodoo2-cards lying around here (from the x86-world) - can I use them or do I need special boards which are designed for the HPPA hardware? Steffen Hein

