trying to understand the interplay between video cards and 3 monitors in linux

[Andrew Farris]

On Sun, 2009-12-06 at 18:29 -0800, Victor Soich wrote:
[snip]
> Will I have enough "power" to run the 3 monitors?  The Memory Size is
> 512MB?  Will the monitors run at "full blast" so to speak.  

Most likely that will be plenty of power....though it depends on what
you plan on doing with these monitors. If you're going to be doing
extensive 3D applications, gaming, etc... then you may want to look at a
card with more RAM...at least 1GB.

> I
> understand I'll have to configure some sort of xorg.conf file, but
> what I'm really interested in knowing is if these two video cards
> working somehow together will be able to power the 3 monitors.  The
> max resolution on the individual card is Max Resolution     2560 x 1600.
>  Since one monitor's resolution is 2560 x 1600, does that imply that 3
> monitors running at 2560 x 1600, won't work with 2 video cards whose
> individual Max Resolution is 2560 x 1600.  Do I have to get more video
> cards, or do I have enough?

Chances are, you shouldn't have to touch your xorg.conf anymore... X is
moving toward a fully auto-configured setup, and their auto-detection of
things like monitor capabilities, milti-monitors, etc has been nearly
flawless imho for a few releases now.

as for the resolution question... it will work fine. The GPU can render
a max of 2560x1600 on each port, so each monitor will have that maximum
resolution. the OS then handles merging those images together to form a
large desktop, or whatever else you plan to do with it.

> These video cards I'm talking about use the NVidia chipset ?  Do I
> have to use the SLI technology from NVidia to run the two video cards
> together?

No... do not use SLI if you want to use 3 monitors. SLI (and ATI's
Crossfire) work by utilizing the unused resources of other graphics
cards to render information on the master card (the others are set up as
slave renderers...similarly to how distributed computing works). The
slaves simply render what they're told, then send it back to the master
card, which splices the images back together, and actually outputs them.
this means that for monitor outputs, you are limited to the number of
monitors your primary graphics card is capable of handling (i believe 2
is the normal max, even on cards with 3 ports...unless it specifically
says you can use more)

for more info, check here:
http://www.slizone.com/object/sli_multi_monitor.html#confoptions

> Furthermore, I'm leaning towards NVidia because they seem to work
> better in Ubuntu linux.  However, from what I can tell,
> ATI is ostensibly, more open source, but their implementation of their
> open source drivers are bad.  Since I'm new to this stuff, I am
> leaning toward NVidia, and hoping it'll "just work" when I finally try
> to install ubuntu linux.  Should I be dissuaded from this, i.e. should
> I go with ATI, or to avoid headaches, should I stick with NVidia?

Actually, I've found that the open source drivers for ATI seem to be
underrated of late... I had great experiences using them, and the only
drawback was that I require 3D support (which the open driver currently
doesn't have), and though it is forthcoming, I didn't feel like
compiling from SVN to get it. I currently am using an ATI HD 2600XT with
dual monitors, and despite the difficulties I've had in the past with
this card, my most recent experiences with it have been a far cry better
than they ever have been before. I can even use ubuntu's 'Display' tool
to configure my monitor, finally... I don't care for ATI's linux tool.

while nVidia seems to have better linux support, lately my experience
has shown the ATI cards under my roof actually have been behaving better
than the nVidias...though on the grand scale, they're about even. The
only thing to watch out for is in the past, nVidia's tool didn't seem to
like saving your resolution settings sometimes (even with the 'run as
root' trick)... and on the flip side, up until ubuntu 9.10, ATI's
configurator didn't like to save the layout/positioning on
milti-monitors (only with the ATI binary driver, and this is no longer
an issue in ubuntu 9.10)

overall, both ATI and nVidia seem to be neck-and-neck on the support
side nowadays, so I think you should be fine no matter which one you go
with.

> I cited specific components, i.e. monitors, and video cards above.
> What I want to do is build a system that runs ubuntu linux with 3
> powerful monitors  ( my eyes suck....)  and I figure I need two video
> cards working together  ( and I don't know if I have to take into
> account NVidia's SLI technology, and/or ATI's Crossfire technology )
> somehow.  I want to know what kind of components I need, so that I
> don't have to worry that I bought the wrong, or not powerful enough,
> cards.  I really don't want the hassle of having bought my video
> cards, and monitor(s), and then having to return them because they are
> not fully supported under linux, and/or not powerful enough cards.

in general, you seem to be in good shape...just dont set up any
SLI/Crossfire and you'll be fine. 

> Anyone who has gone through this "hassle" of trying to get 3 monitors
> to work in ubuntu linux, please steer me clear of "bumps in the road".

if you're using ubuntu 9.10, then I wouldn't expect many issues, if any
at all. Just be aware that if you need 3D support, don't use the open
drivers...

Also be aware that there doesnt currently seem to be any way to play 3D
games on just 1 monitor (it just clones output if the game doesnt
support the higher virtual resolution, or turns the monitor off in the
case of Wine-games).

Hope that helps


-- 
Andrew
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