cannot change gamma on 855GM

[Yves Grenier <grenier.yves@wanadoo.fr>]

Hello,

I installed debian sarge (i.e. testing) on an A3N15 Asus laptop, the 
graphic chipset is 855GM. The display looks as if the gamma was set to 
3.0 or more. Using KDE configuration tool produces no effect, except 
writing into XF86config-4 a line "Gamma 1.0" in Section "Monitor". I 
also tried xgamma, and it produces no effect on the display.

Any idea of a solution?

My configuration:
XFree86: 4.3.0.1 (driver i810)
kernel: 2.6.9

Yves Grenier