[Openchrome-users] Widescreen Resolution

[userforum@openchrome.org]

Re: Widescreen Resolution

Hi,

i found a way to get own resolutions working. :-)

So answering myself, hoping it helps other people.

I do not know the reason why, but the driver (hardware??) only excepts a fixed set of dotclocks. So if you want to define own modelines you have to create ones which have exactly one of the fixed dotclocks. 

1. Download the following tool and compile it with gcc -o modeline_dot  modeline_dot.c:
http://www.dkfz-heidelberg.de/spec/linux/modeline/modeline_dot.c

2. Pickup a dotclock from the via_mode.h from the driver source (from the ViaDotClock array, the values in the first column are the dotclocks)

3. Use the tool to calculate a modeline, with width height dotclock/1000 for example:
./modeline_dot 1680 1050 148.5

Horizontal Resolution:  1680
  Vertical Resolution:    1050
  Dot Clock Frequence:    148.50 MHz
  Vertical Refresh Rate:  59.80 Hz
  Horizontal Refresh Rate:65.13 KHz

 # V-freq: 59.80 Hz  // H-freq: 65.13 KHz
 Modeline "1680x1050" 148.50  1680 1760 1944 2280  1050 1050 1052 1089

4. Try with different dotclocks until the values for the refresh rates (horizental/vertical) are ok for your panel / monitor

5. add the modeline to your xorg.conf

If it does not work look at the Xorg log, maybe there is a limitation with the chipset, for example for my KM400 the maximum dotclock is 150000 (reported by Xorg.log)

Disclaimer: Try this on your own risk, I am not responsible for any damage this recipe may cause.

Maybe the tool can be integrated into the driver, so that it calculates modelines on the fly at X startup, making all reslutions possible. 

Hendrik