On Tue, 13 Nov 2001, Robert Baruch wrote:

>  > > Why is the server changing my modeline?

>  > The ATI driver purposely does not allow changing the panel's dot clock.
>  > In addition, in a dual output situation (i.e. DFP and CRT), both outputs
>  > will always see the same timings (and image).  Among other things, this
>  > means the CRT should sync to the same timings as the panel.  If it
>  > doesn't, as is likely the case for 1400x1050 panels, you are limited to
>  > using only one output per X server invocation.  And, for CRT-only, you
>  > need to specify Option "CRTScreen" in your XF86Config.

>  > The driver enforces these restrictions to avoid system lockups.

> OK, I can live with the LCD and the CRT having the same timing. I'll
> just set the resolution to 1280x1024, which both LCD and CRT can handle.

> However, you say that the ATI driver doesn't allow changing the panel's
> dot clock.

> According to the XFree86.log:

> (--) ATI(0): Panel clock is 107.859 MHz.

> Fine, if it wants a dot clock of 107.859, I'll give it that dot clock in
> XF86Config-4:

>          Modeline "1280x1024va" 107.859
>                  1280 1328 1440 1688
>                  1024 1025 1028 1066
>                  +hsync +vsync

> However, the driver still changes the timing parameters of the modeline:

> (**) ATI(0): Mode "1280x1024va": 107.9 MHz, 58.4 kHz, 53.9 Hz
> (II) ATI(0): Modeline "1280x1024va"  107.86  1280 1328 1456 1728  1024
> 1024 1027 1056 +hsync +vsync

> I doublechecked the horizontal and vertical rates that my modeline
> specifies to make sure it doesn't exceed the capabilities of the monitor:

> 107859 kHz / 1688 = 63.90 kHz
> 63900 Hz / 1066 = 59.94 Hz

> This is within range of the monitor:

>          HorizSync   30-82
>          VertRefresh 50-75

> So why is the ATI driver changing my modeline?

The driver stretches the mode to fit the panel.  Both outputs see the
timings as they are >after< stretching.  In effect, barring option
"crtscreen", both outputs always see the timings of the same mode.  This
mode is called "Native panel mode" and is internally generated.

Marc.

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