[Lvlug] Duall headed system, was: Prolonging the Life of a Hard Drive?

[Mark]

On Monday 05 September 2005 11:02 am, Randy Kramer wrote:
> Looking at a Matrox G450 (which I can get for about $15 used, now), it uses
> Xinerama and thus X, at some level is aware of two screens.  I'm concerned
> therefore, that the performance may not be quite the same as the Nvidia.
>
> What are your experiences / thoughts?

Jumping in with a Long Story.

I was initially running a dual headed system with an NVidia card that had 
twinview support (works at the hardware level) as you described above.  
Something happened to that computer and I believe the video card too, because 
the twinview quit working.  I never went back to test whether it was the card 
or the motherboard that had failed but the machine finally gave up the ghost 
about a year later.  Since I had become hooked on a dual headed system I had 
to find a way around the problem.  So for that year I kept the NVidia card in 
the AGP slot (It still functioned as a single output) and added a PCI video 
card (Matrox Millenium) in another slot.  I was able to get things running 
smoothly and there was no delay between the two screens. The only problem I 
ran into was some serious video corruption on the PCI card.  Turns out it was 
only a 2Meg video card and everything was fine when I replaced it with an 
8Meg.

One of the major drawbacks with using the two card method above is that you 
will not be able to use 3D accelerated video. Even though you may be able to 
install the drivers your system will never use anything more than 2D   
accelerated video.  The 3D driver access to the video cards is at too low a 
level for X to be able to use it and is incompatible across the two busses.  
It is best not to use 3D drivers if you can help it.  As an example I used 
the built in nv drivers instead of NVidia's 3D drivers.

Recently I was able to get a new computer and when I set it up I got another 
NVidia card capable of twin output. It is a PCIX card with an analog and a 
DVI output.  In twinview the card is only capable of dual analog output but I 
have full 3D acceleration.  The MatrixGL screensaver kicks! And looks really 
great on the two 19" widescreen LCD monitors that I got for my new system.

Setting things up for the two card method is not that difficult but will 
almost always require that you hand hack the /etc/X11/xorg.conf file for best 
(any?) results.  Probably the easiest way to do it is to setup each card 
individually and manually merge the two config files if you are using older 
hardware. However, with the later versions of XOrg and XFree you can simply 
plug in both cards, run xorgsetup (or XFree86 -configure) and then make any 
changes to the config file after that.

Remember this!  /var/log/Xorg.0.log is your friend!  I was setting up my 
system and was banging my head against the wall until I looked through all 
the warnings in the log file. As I read the log I would fix the first problem 
I found and then rerun xorgsetup.  After three tries I had worked out all the 
bugs for the minimum needed configuration to get things working.  I later 
went back and turned on 3D acceleration, hardware mouse and shadow and a 
couple of other features I wanted.

The results are worth the effort. If you have any problems try posting your X 
config file and the log file.

-Mark