Xorg-6.8.1 / ATI & DDC function

[Valery]

Hi,
i would upgrade Xorg-6.7.0 to 6.8.1 in order to
try to correct a seemingly malfunction with ATI
video card and the set {ati,radeon_drv,drm} modules.

The trouble we encounter is a bad setting of
the DCF (Dot Clock Freq.) of the ATI Card at
X startup. The result is a very high Moiré-Effect
with LCD monitors, making them unusable at their
optimal resolution.
We target the drivers because we don't have any
problem with other OS (MS ..)
Of course, changing cables and so one has no effect.

We have tried to setup our proper modeline, at
different frequencies but the driver seem to do
what it want : modeline values don't give expected
monitor frequencies.
For example, this modeline :
"1280x1024" 108.00 1280 1328 1440 1688 1024 1025 1028 1066 +/+
should give you a HSF (Hor. Freq.) at 63.9KHz,
but the monitor report a HSF=64.7Khz ; we don't
know how the driver and the video produce this difference.
Generally, you got a little difference arround 0.1~0.2KHz,
but not 0.7, it's a big one.
Other OS have a good behaviour (monitor report
the good frequency, and there's no Moiré Effect with
of course same resolution).

We have upgraded radeon_drv from 4.0.1 to 4.4 with
no effect.
We have emailed to Gatos (ati,radeon_drv), and they advice
to update Xorg to 6.8.2.
We have emailed to some "Video veteran", and they don't
understand.

The set {Xorg6.7, ati6.5.6, radeon4.0.1} had a problem
with DDC (no DDC detection), and we hope our solution
is here, Xorg6.8.1+videoDrivers seem to correct
that (release notes).

Well, this problem concern 6 computers, and we need
a solution, no matter to change monitors neither computer.

Has anybody some advice or some information about that ?
Ho, we use FBSD-5.3

Many thanks,

v/