X on a Toshiba Satellite Pro 4600

I have a old Toshiba Satellite Pro with the following graphics adapter:

# lspci

...

01:00.0 VGA compatible controller: Trident Microsystems CyberBlade/XP (rev 63)

...

As Operating System I use Slackware 13.1. The display I use for this notebook is a LG Flatron L1919S. The Problem was when I start X I only got an resolution of 800x600. After searching I found this simple xorg.conf, added the values for HorizSync and VertRefresh for my display and now everything is fine:

# vi /etc/X11/xorg.conf

Section "Device"
        Identifier      "Trident Microsystems CyberBlade/XP"
        Driver          "trident"
        Busid           "PCI:1:0:0"
EndSection

Section "Monitor"
        Identifier      "Monitor0"
        Option          "DPMS"
        HorizSync       30-83
        VertRefresh     56-75
EndSection

Section "Screen"
        Identifier      "Default Screen"
        Device          "Trident Microsystems CyberBlade/XP"
        Monitor         "Monitor0"
        DefaultDepth    24
EndSection

Section "ServerLayout"
        Identifier      "Default Layout"
        screen          "Default Screen"
EndSection