display problem after installing OpenSuse 11.3 on an old laptop

Fixed problem with display setting/screen size on old laptop

I own an old laptop with Pentium 4 processor (Gericom WebGine Per4mance XL). I had to install Linux since my usual laptop is not working.

After installation of Linux OpenSuse 11.3 the GUI started correctly, using the full screen (1024x768).
I did the OS actualisations as proposed, later switched off the computer.

Next day, the startup Linux screen used full screen, but when the GUI was starting (X11), only part of the screen was used (about size 900x600), which hurt me much. I first searched for a YAST (system configuration) module to change the display size, but could nor find it in the “Hardware” section (since the tool “Sax2” is not available in OpenSuse 11.3 any more). When I finally found somewhere else a menu where I could change size and resolution, it did only offer low resolutions.

Finally I executed command “xrandr” as in a console window: it had mode lines only for low resolutions, but not for my desired resolution.
This is my solution:

Start yast control center / hardware / hardware informations
select section: monitor / display : I got the frequencies for the monitor SIS 650 (VGA)

height 768 width 1024
horizontal frequency: 31-61
vertical frequency: 50-90

I then executed command in a console window:
cvt 1024 768 50 # (xsize=2014, ysize=768, refresh=50 in allowed range)
and got the mode line
Modeline “1024x768_50.00” 52.00 1024 1072 1168 1312 768 771 775 793 -hsync +vsync

Now edit /etc/X11/xorg.conf.d/50-monitor.conf (as root user), put in the new mode line and also put in the HorizSync and VertRefresh limits as below:

Section “Monitor”
Identifier “Default Monitor”

If your monitor doesn’t support DDC you may override the defaults here

HorizSync 31-61
VertRefresh 50-90

Add your mode lines here, use e.g the cvt tool

Option “Preferred Mode” “1024x768”

1024x768 49.98 Hz (CVT 0.79M3) hsync: 39.63 kHz; pclk: 52.00 MHz

Modeline “1024x768_50.00” 52.00 1024 1072 1168 1312 768 771 775 793 -hsync +vsync
EndSection

Restart your GUI (change to runlevel 3 and then 5 again, or simply restart computer).

I hope this helps someone else, it cost me hours.
Only thing missing: how could I use an external monitor? Probably I would have to edit the xorg.conf files manually.