> This is my xorg.conf which works on the 4.4 snapshot I was running.

quoted text
> Unfortunately I can't get three screens going, and the 4.5 snapshot I

> tried to upgrade to on Friday is currently crashing on startup, so I

> can't tell if it's any better yet. This may well be a factor, as my

> xorg.conf is pretty straightforward :

Unfortunately I have to inform you that months and months ago X.org

broke multi-card X for everyone, and they have not fixed it yet.
Until they fix that, you can only use one video card.
They have shown strong reluctance to fix the damage.
Go to their mailing lists and complain.