Re: What driver version does 1080i properly?
Josh, you are right!
Now that the latest driver (8178) is avalible for gentoo, I emerged it, fired it up, and sure enough I can do 1080i without the split screen bug. I have no idea of how overscanned it is yet, but the last my last piece is in place, so the box goes down to be connected to the HD set tommorow. I'll find out about any overscan then.
To sum up the answers to the questions in this thread: the 6299 driver doesn't support the Geforce 6200 series cards, the swap/screen in interlaced mode bug started in the driver version following 6299, and has apparently been fixed in the new 8178 driver.
Looks like I picked just the right time to be working on this. Had I been doing this a month ago, I would have hit a wall...
Thanks for all the help!