4.1. Do I need a modified X server?


For some video cards you can skip this part. Before installing the modified X server check the Video Compatibility list to determine whether you need one. Currently there are reports for working configurations without using a modified X server for Voodoo Graphics as primary and Voodoo3 or Nvidia TNT2 as secondary.

"Why should a modified X server be used?" - The reason is that XFree is designed to serve a single user and this design requires a single X server to drive all available graphic cards. So when an unmodified X server starts, it disables access to graphic cards for other X servers. Hence we have to modify XFree to make it possible more then one X server to run at the same time.

If you decide first to try without installing a modified X server, follow these steps:

  1. To enable this feature you have to add this to your XFree configuration file:

    Section "ServerFlags"
    Option "PciOsConfig" "1"

  2. and to inform the kernel to filter unnecessary PCI commands:

    [root@mc contrib]#echo  "1"> /proc/bus/pci/hackvideo

  3. If you want this to be done automatically on every boot you have to add :

    if [ -x /proc/bus/pci/hackvideo ];then
          /bin/echo "1"> /proc/bus/pci/hackvideo

    to your init scripts, preferably somewhere at the end of /etc/rc.d/rc.sysinit (so the command is executed before X is started)

  4. If you want to disable this functionality you have to:

    [root@mc contrib]# echo "0"> /proc/bus/pci/hackvideo


This functionality exists in the Backstreet Ruby kernel since 15. May 2003 and in Ruby-2.6 since 29. Sep 2003 , but will never be added to the official linux kernel as it is a small hack to spare you installing modified X server.

It is still recommended to install modified X server.