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Infodoc ID		Synopsis		Date
17131		How do I add an additional head (framebuffer) to my system?		20 Jan 2000

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How do I add an additional head (framebuffer) to my system?
===========================================================

Adding an additional head to a system is quite easy.  Before OpenWindows 
v3.2 (Solaris 2.2) there was a limit of 4 heads supported by the xnews server.  
With v3.2 this was raised to 16.  However, the effective limit is dependent
upon the physical limitations of a particular system.

In order to add an additional framebuffer, follow these steps.
	
1) touch /reconfigure
2) halt the system
3) power off the system
4) Install the framebuffer
5) reboot the system.  It should perform a re-configuration boot (due to the 
   existence of /reconfigure).

How do I start OpenWindows in a dual-headed configuration?
==========================================================

You will need a machine that has two frame buffers correctly installed,
together with matching monitors. The frame buffers do not need to be
identical; there are several advantages in having each screen running
on entirely different framebuffers.

The component that controls the screen is the X server, Xsun. This is started
automatically when you invoke openwin. Openwin will pass flags and options
down to Xsun to tell it how to configure the displays. The flags needed are
detailed in the Xsun manual page.

Take as an example a machine which has two GX's installed. Looking in /dev
you  should see the following: 

      /dev/fb is a symbolic link to the frame buffer entry in the devices 
directory:
      /devices/sbus@1,f8000000/cgsix@1,0:cgsix0. 
      /dev/fb0 and /dev/fb1 are links to entries in the directory /dev/fbs,
in this case
      /dev/fbs/cgsix0 and /dev/fbs/cgsix1. 

To start up a multi headed configuration you must specify each device you
wish to use using the option -dev, thus: 

        openwin -dev /dev/fb0 -dev /dev/fb1

For a 3 headed system, this would be 
    openwin -dev /dev/fb0 -dev /dev/fb1 -dev /dev/fb2
 
  The order that you give them is important for two reasons; display zero 
machinename:0.0 comes first, then display one machinename:0.1 and so on. By 
default they are ordered left to right; to change the order you can use the 
keywords left, right, top or bottom. Thus the commands: 

        openwin -dev /dev/fb0 -dev /dev/fb1 left
        openwin -dev /dev/fb1 -dev /dev/fb0

will start up OpenWindows with fb1 on the left and fb0 on the right, but in
the first instance fb0 will be logical screen 0, and in the second it will be 
screen 1.

The keyword tells the server where to position the current display relative to 
the previous one, so any keyword placed after the first device is ignored. If
no keyword is given, the default is right. Thus the command: 

        openwin -dev /dev/fb0 top -dev /dev/fb1

will not have the desired effect; you would need to use: 

        openwin -dev /dev/fb0 -dev /dev/fb1 bottom

Other keywords can be used after the device name to control such things as 
default depth or visual; these are discussed in the manual pages and are
beyond the scope of this document.