LinuxQuestions.org - Does RandR 1.3 support multiple video cards?

I have a fedora13 installation with two nvidia cards (NV34GL and NV37GL, both dual head) that I'd like to get running driving 4 monitors. Nouveau and randr 1.3 are happy driving two monitors from a single card, but I cannot find any definitive information on whether randr 1.3 supports multiple video cards.

I have one card in the PCI:1:0:0 position and the other in the PCI:3:5:0 position. It is interesting that the outputs that work are connected to the 3.5.0 card and that they are named DVI-I-3 and DVI-I-4. This suggests, to me, that randr "saw" the 1.0.0 card and assigned the DVI names -1 and -2 to the outputs on that card. However, xrandr only reports:

Screen 0: minimum 320 x 200, current 2560 x 1024, maximum 4096 x 4096
DVI-I-3 connected 1280x1024+1280+0 (normal left inverted right x axis y axis) 376mm x 301mm
1280x1024 60.0*+ 75.0
1152x864 75.0
1024x768 75.1 60.0
800x600 75.0 60.3
640x480 75.0 60.0
720x400 70.1
DVI-I-4 connected 1280x1024+0+0 (normal left inverted right x axis y axis) 376mm x 301mm
1280x1024 60.0*+ 75.0
1152x864 75.0
1024x768 75.1 60.0
800x600 75.0 60.3
640x480 75.0 60.0
720x400 70.1

If I create an xorg.conf file and try to put both card definitions in separate Device sections, the displays don't come up. I just get a black screen into which I can type anything and it gets echoed to the screen. I can get a virtual console with alt-F2 no problem. Also, if I ctl-alt-del to reboot, the black screen disappears to show what appears to be a fully functional X session running behind it. Of course, I can't access it since the system is shutting down.

Can I do what I want without moving back to the proprietary nvidia drivers?

Thanks,
Marc