Phoronix: Multiple X Servers For One Graphics Card, Again
One of the long sought after features of X.Org and the Linux graphics stack has been the ability to run multiple X Servers from a single graphics card. While this wouldn't be used by many, there are still many interested in seeing this feature request become a reality...
it said in the article - multi-seat configurations.
however, it would be better for multiseat to be feasable on single X. for normal non-xrandr multi-screen configuration your still need two X video driver instances inside one X anyway.
it could be much better to make it possible with single driver instance and inside one X so you could dynamically reassign input devices and output ports to seats. maybe even going further and making it possible to control multiple outputs of multiple cards from same X and reassing them dynamically too. ah, dreams...
Why not just create the concept of binding a mouse and keyboard to an Xorg.conf "Screen" and then all you need is a multi-head configuration (i.e. multiple X screens not bound together with Xinerama). You can have different Window Managers running and all applications will work appropriately because $DISPLAY is set separately.
ATI and NVIDIA support this with each output and ATI cards support this up to 6 outputs a head multiplied by however many PCIe slots you got. You get full acceleration as well.
The changes would have to go in the input side of the X world but since it's not as sexy as the proper X side, nobody is going to jump to do it.
Of course, the other option is to wait for "Multiple X Servers for One Graphics Card" to be resolved.... again.
First of all there are multiple uses for multiseat/multi x server configs like:
Splitscreen gaming for games without splitscreen support
Gaming on one screen while chatting on the other without switching
Multiuser classrooms/workstations - its more efficient to have like one powerfull workstation sharing power when needed than having 6-10 cheap nettops/stanadrd workstations + administration of this is easier
Other uses that would need constant mouse focus on each screen.
As for multiple xorg instances on one card the problem is that for standard each xorg instance needed different device pci address so it worked only with cards like D-SUB + DVI with splitter/converter or sth like this so DVI was for example 02.00.00 while D-SUB had 02.01.00 or sth like this.
Anyway if You ask - why can't u just get another card? The answer is simple - multiple vga's would bring serious heat and would need serious power and it doesnt get anywhere near efficient power use and additionally ofcourse the solution as a whole wouldn't be cheap.
Most of cards now have in standard 2xDVI + HDMI(which can be converted to DVI easily) so for 10 user multiseat we would need only 3 cards and motherboard with 3 pci-e X16/X8 and integrated gpu witch is nearly becoming a standard for today while having 10 vga's is almost impossible without extension boxes like quadro plex(Check the prizes )...