Hi,

I upgrade my RiscPC from 1 to 2MB VRam. On the RiscOS side all is fine, but
on the NetBSD side many screen modes only produce rubbish. Screen modes
that still work are 640x384, 640x400, 640x480 and 1024x768. Screenmodes
that don't work are 800x600 and 896x672. The strange resolutions are because
I compiled my own kernel with own video modes, but all problems are also
with other kernels from ftp.netbsd.org as far as the screen modes are
existing.

In one of the not working screen modes the characters look like:

Looked with 1MB VRam:                     Looks now with 2MB VRam:
        
           00       1     2222            0       1      022            22
          0  0     11    2    2            0      1     0   2    1     2
         0    0   1 1    2    2             0     1    0    2   1      2
         0    0     1         2             0     1    0    2
         0    0     1       22              0     1    0  22
         0    0     1      2                0     1    0                 2
         0    0     1     2                 0     1    0                2
         0    0     1    2                  0     1    0               2
          0  0      1    2                 0      1     0              2
           00     11111  222222           0       111    0222   11     222
           
           
 1a  1b  2a  2b  3a  3b  4a  4b            2b  1a  3b  2a  4b  3a  5b  4a


But in about the first left 50-100 pixels this scramblin happens only in
about every second pixel line.

Also in video modes that work the screen sometimes flickers.

So my question is: Why does all this happen? In RiscOS I have no problems
with these screen modes. It seems that the VIDC is programmed in a wrong
way which sometimes works, but not always. Perhaps it is only a timing
problem, as the flickering that sometimes happens looks like the flickering
caused by a too high pixel clock under RiscOS.

Another problem is that I could not get X running in 16M colours. 256 and
32K were no problem (if I used a working screen mode) but trying 16M simply
crashed the whole machine.

Is there a possiblility to fix these problems? I would be really interested
in it because otherwise I had to think about buying a cheap PC box.

Thank you very much in advance for your help!

-- 
Peter Teichmann

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Email: teich-p@rcs.urz.tu-dresden.de  WWW: rcswww.urz.tu-dresden.de/~teich-p