First, the really
good news - "pci=nommconf" eliminated the video lockup problem, that bit's just fine!
Next, running the nvidia-xconfig line you mentioned does generate a file that runs all four screens. With a couple of issues - not sure if these are things I can configure around or not:
- I have one 19" FP that I want in the center of three panels. There are two 17" FPs that flank it. I was going to put the 19" on the first card, and the two 17"s on the second, but I don't think I can split the TwinView screen around the center panel?
- The two monitors that were on the first card had the menubar stretched across both screens - as I expected, since X sees it as a single large monitor, although I would prefer to keep it only on one panel. When I would maximize apps they went "fullscreen" across both panels as well. Can that be accounted for somehow?
Related to that first, is it even an issue whether I have one of the side panels on the same card as the center? I was thinking perhaps I'd get a little better performance if it was by itself, but what I have right now is so much better than anything else I own I probably wouldn't miss it...!
When not using TwinView, I do now have a working three-panel config, which is satisfactory although I would certainly like to get the fourth output usable. By putting just one monitor on the second card, X picks it up just fine. It's only when I add the second Device section for that card that it says "No matching Devcie section for instance (BusID PCI:8:0:0) found".
Thanks for the help! The bug report log when trying to run a quad-display non-TwinView setup is attached.