radeon: different colors on different heads?

[Csillag Kristof]

Alex Deucher wrote:
> Does adjusting the gamma on the problematic head help?

If I understand your question correctly, you suggest that the gamma
correction function might be off.

I don't think this is the case, because on my monitor, the relation
between (at least) the blue part of the pixel data and the actually
displayed color seems to be a non-monotonic function.

See the photo I made about the color selection dialog from GIMP.
(Before taking the picture, I stretched it out horizontally for best
visibility.)

On proper head:
http://picasaweb.google.com/lh/photo/OB7B3DgO3LKLmL4NUxx5Jw?authkey=Gv1sRgCM60oc7kuoW24gE&feat=directlink

On bogus head:
http://picasaweb.google.com/lh/photo/ZRIy7uJmmPmVWxEcSmVTKg?authkey=Gv1sRgCM60oc7kuoW24gE&feat=directlink

The current setting is 0000FF (RGB), and as you can see, the gradient
from 000000 to 0000FF (the 6th line, besides letter B), and
the one from 0000FF to 00FFFF (the 5th line, besides letter G)
are messed up in creative ways. (They should be monotonic, but they are
not.) As far as I can tell, wrong gamma does not do that; it does not
introduce non-monotonic transformations.

It looks almost as if some bits of the blue data were sometime lost in
transition. (But where?)

Thank you for your help:

   Kristof