From Newsgroup: comp.sys.ibm.ps2.hardware
Not sure the Multi-Head includes the XGA-NI.
https://ardent-tool.com/AIX_1-3/AIX_PTF0024_U436295.html
SMALL PROGRAMMING ENHANCEMENTS (U436295):
IX44820 X11R5 multi-head support and S3 SVGA 1024x768x256 color support.
Multi-Head Support For X-Server
The new AIX PS/2 X Windows and Motif supports multiple display
adapters (multi-head) with seamless movement of mouse across displays. Currently the X-server can support up to 8 display adapters, though
more than one instance of the same adapter is possible for XGA only (by hardware design). All other adapters (VGA, 8514/A, Image Adapter) can
only have one instance in the system. It is possible to have up to 8 instances of XGA in the system.
The multi-head support is only supported on the PS/2 (MC bus) only,
and is not available on the ISA bus. This is because of the lack of
multiple video card support on the ISA bus.
The following options were added to the X-server for multi-head support
-all Runs the Xserver on all available displays.
(This does not include the planar VGA, if available.)
e.g xinit -all
-allp Runs the Xserver on all available displays,
and the planar VGA port on systems like model 80.
e.g xinit -allp
-P<r><c> <display no> {/vga} | <display name> {/vga}
(where words enclosed by {} are optional)
This option is used for specific placement of displays. The
utility (see defect 531) lsdisp, displays the displays cards attached to
the system with a display number and the name of the display. The
numbers <r> and <c> denotes the element in the placement matrix where
the display will be placed for the sake of cursor movement. for example
a matrix of 4 displays can be specified with the following row and
column numbers.
----------------
| | |
| 11 | 12 |
| | |
---------------
| | |
| 21 | 22 |
| | |
----------------
This means the cursor can have a seamless movement from
11 to 12, 11 to 21,
12 to 11, 12 to 22,
21 to 11, 21 to 22,
22 to 12, 22 to 21 .
Of course, the movement can be four-directional without any bound using
-wrap option,
or vertically/horizontally without any bound using
-wrapy / -wrapx options.
When using the /vga option with the display number
or the display name, the display can be run in 640x480 16-color VGA mode.
e.g
For instance, if there are two display cards
installed, an XGA and a 8514/A, with XGA as display number 1 and the
8514 as display number 2, X can be run as follows:
xinit -P11 1 -P12 2
or
xinit -P11 xga -P12 8514
or
xinit -P11 xga -P12 8514/vga
This will run the 8514 in VGA mode and the XGA in XGA mode.
Note: only one instance of VGA can be specified.
Note: To get multiple XGA adapters to work, the last XGA adapter on the
system should have its 1 MB VRAM aperture disabled. This can be done
using the reference diskette. If the 1 MB VRAM aperture is disabled to
run X in XGA mode, the system will try to use the 4 MB VRAM aperture.
Using the 4 MB VRAM aperture is only possible when the adapter is
plugged into the 32 bit slot. There are only 3 such slots on the model
80. Therefore, it is possible to have a VGA and up to 3 XGA or XGA-2
adapters on a model 80. (The last card is determined by the adapter slot number and the adapter order shown when the configuration is viewed with
the reference diskette.)
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