I have a pair of 1440 x 900 monitors that I want to run in portrait mode (not mirrored).
When I select 800 x 600 for both, it works, but I am not near the maximum of the monitor hardware nor am I near what appears to be the addressable space of 1600 x 1600.
If I select 1280 x 800 for both, I get the following error:
The selected configuration could not be applied: requested position/size for CRTC 148 is outside the allowed limit: position=(800,0), size=(1280,800), maximum=(1600,1600).
Superficially it appears this error is a bug. A pair of 800 pixels side by side (when in portrait) does not exceed 1600, and of course 1280 does not exceed it.
How can I get this to work. Of course I would prefer a pair set to 1440 x 900 which is the actual LCD resolution, but then of course the 900 side by side pair would total 1800 and so I won't even bother with that.
The correct rotation setting seems to be "counterclockwise". I am using Ubuntu 11.10 and a Radeon HD 5450 and the Catalyst 11.12 for x86-64 architecture. I am dual booting. I had no complaints with the visual quality on Windows 7, it looked good and used the natural resolution (1440 x 900) even in portrait. Thus it seems safe to conclude the hardware can do it but Ubuntu and the driver for Ubuntu is at fault.
Although it would be a shame to do so given the Windows 7 example, I would be willing to buy a new video card if a card and driver combination successfully displays dual monitors in 1440 x 900 (each) non-mirrored portrait on Ubuntu 11.10. Please post a comment if you have this working. At this point I would even consider landscape non-mirrored dual monitors.