Forum OpenACS Q&A: OT: Anybody have pointers on Linux/XFree86 Multi-Monitors?

I've just installed Mandrake 7.2 on a former Win98 box (well, maybe
not so former) and I can't find anything about support for multiple
monitors. The box in question has a Voodoo Blaster and Matrox Milli,
but I'll buy another card just to get the productivity gain.

Has anybody had any success with multihead support? I'd really like
to put linux multihead on a laptop, but the desktop comes first.

I saw the XFree86 guys running multi-headed at the Linux Pavilion at Comdex in Fall 1999 on a box with three Matrox PCI cards; it works. Multi-head configuration is discussed in the XFree86 4.0.2 release notes (RELNOTES). You identify the device with BusID. ServerLayout will describe how many heads, etc. This is all configured in the XF86Config-4 file on my system; I believe the example XF86Config-4 file that is installed has an example of a multi-headed system.

The Matrox Millenium G400 and G450 cards should be fine (there are two heads on one AGP 4x card). The G450 is my recommendation because the secondary head has a faster RAMDAC than the G400 (the primary heads both use 360MHz RAMDACs).

Sadly, I don't have an actual configuration file for a multi-headed system since I haven't ponied up the $550 for another Sony G400 monitor.

I'd really like to put linux multihead on a laptop, but the desktop comes first.

Generally speaking, laptops aren't equipped for multi-headed operation. If you are thinking you can plug in a monitor into the VGA plug in the back and run one head on the laptop's display and another head on the external monitor, this won't work.

When you press that function key switch, you are not cycling graphics heads. You are simply enabling the onboard auxiliary video DAC and outputting the display buffer through the analog pipe. A few of the better laptops have graphics chips that will display at higher resolutions on external monitors than the native display.

It is possible that a few of the newest laptops have true multi-head capability, but they will be clearly labelled as such. I briefly looked at the laptops on Dell's site and I don't see any claims of multi-head capability. I don't follow PC hardware closely (particularly laptops), but if this can be done, there will be a FAQ, HOWTO, whatever out there. Use Google to find out where it is.

Concerning the Matrox Millenium Gxxx series: Matrox releases their own unsupported "beta" Linux drivers on their web site. The readme.txt file includes detailed instructions on the usage of their driver; included are relevant config file code fragments for multiple head configuration.

When I was fortunate enough to work for ArsDigita in the UK, we had the multi head configuration working for the G450, there was some problems with crap being displayed @ high resolutions but it worked.

Also I think the graphics card in my laptop is Multihead (have Dell Inspiron 5000e), well @ least Windows ME reports that I can multihead, but I blasted ME and installed Debian where multihead under 4.0.2 does not work.