When using the Radeon X1950PRO with the Avivo driver we had noticed some odd behavior with an Acer AL2223Wd LCD monitor. The screen resolution (1680 x 1050) was properly detected and the Avivo driver was set to 1680 x 1050, but there was a problem experienced with GNOME, which is shown below. With some of the other GPUs the monitor screen resolution had reverted to running at 1360 x 765 while in other cases we had no problems.
The basics of RandR 1.2 had also worked when using two LCD displays with the ATI Radeon X1800XT 256MB and the Avivo driver.
While the Avivo driver is only a week old for the public, this open-source driver comes after months of work and there is still a long road ahead before this driver reaches a comparable level of support to the Radeon R200/300/400 and Nouveau open-source drivers. Right now this driver is only desgined for developers and those wishing to test and experiment with the code. It's pleasing to see the initial RandR 1.2 support so soon and that the driver, which ultimately should support the entire R500 and R600 GPU families, making good progress. As new features with the xf86-video-avivo driver develop, we will have additional articles and share other highlights about this latest open-source driver.
You can discuss the open-source X.Org Avivo driver in the Phoronix Forums.