Thinkpad T41, Ubuntu Radeon driver
Ubuntu ran fine, except for video performance, using the supplied driver.
Searching for ”radeon” in the program central found
Video driver for the AMD Radeon and FireGL graphics accelerators
I installed this and video performance is now basicly good.
Maximun resolution on secondary screen is stil 1024 x 768.
Edit. HD video is still beyond it’s capabilities but that is understandable on such old hardware. Nice to find a Linux fix that does not require rocket science.

