Multihead Video card with multiple hardware addresses?

[pipsey]

Hi all, I'm a co-op for the IT department at my university and I have a little project I'm working - a multiseat Linux workstation for some software development we're working on. The basic concept is four keyboards, mice, and monitors, each with a separate graphical login. The problem is, X windows doesn't like handling multiple monitors in this way if the video card only has one address for more than screen - why technically I'm not exactly sure, but the howtos and other instructional sites I've read out there seem to agree on this. Most of the multihead examples were using multiple PCI video cards, but we would prefer two dual-head PCI-E cards for this setup. However, I'm having trouble finding a video card that has two heads and a separate PCI address for each head, because that particular bit of info about a video card seems too arcane to simply google it.

Given all that, does anyone know of a dual-head crossfire or SLI compatible video card that has a separate address for each card? Or, perhaps, a way to work around this issue using a more "normal" video card? Thanks in advance

 

[xtknight]

Hmm, I'm confused. Let's clarify:

You have four monitors...
You want four X screens...

What is wrong with using the conventional dual monitor methods (via "nvidia" drivers for example) but doing them for two devices? Why does it need more addresses?

By address, do you mean PCI Bus address?

Er, thinking...so you want four actual workspaces, one per monitor, right? I believe that's called "Separate X Screen" mode under nvidia-settings.

Look here: http://us.download.nvidia.com/XFree86/L...x86_64/1.0-9746/README/appendix-p.html

 

[pipsey]

Sorry, I knew that was going to sound like a bunch of confusing garbage, but I was having trouble clarifying what I needed into words.

I have four monitors, four keyboards, and four mice. What I want is four separate X sessions with graphical logins (rather than console), so that four people may be working on the same (very fast) machine at the same time. Most guides for a setup like this have four separate video cards, but we'd like to do it with two.

I did mean PCI Bus addresses. Both people in the gentoo chatroom and the few guides that actually mentioned dual-head video cards said that I would need a card that would assign a separate bus address to each head. I was planning on manually editing xorg.conf to achieve this result, as it seemed the most flexible option.

Sorry for the confusion. Software is more my realm than hardware, and while I'm fairly good with Linux I'm no pro there either.

 

[xtknight]

If you have an NVIDIA card to test you could try the link above. Actually, I'll give it a shot on my setup and see if it works. But, currently I only have one NVIDIA card.

 

[pipsey]

The card I presently have is a Radeon X1650PRO 512MB using the closed-source fglrx driver. Right now I'm using one card and trying to get two separate screens before we buy the hardware for the real deal. Works fine with a standard setup, but if I try to do a multihead X complains that the card is already in use.

*quick edit* That setup is very similar to what I have done already, but it didn't work. I may try it again as I may have messed something else up.

 

[pipsey]

Well, I was able to get the monitors to behave separately, however locking separate keyboards and mice to them is indeed impossible without separate PCI bus addresses, as per http://gentoo-wiki.com/HOWTO_Multiseat_X

If it's possible to do what I'm looking to do without multiple addresses I have been looking at the wrong guides. The one you showed just shows how to make the other monitor usable separately, similar to the "extend my desktop" option in windows, except you can't drag windows from monitor to monitor. Looks like I'm going to need a card with multiple PCI bus addresses after all.