[[!summary chatGPT: The author encountered a limitation in the Radeon X300 graphics card where only one crtc interface could be used at a time, leading to a workaround using the xrandr command to disable and enable outputs, and suggested improvements for error messages.]] [[!meta date="2009-10-26 11:29"]] [[!img media/t43-radeon.png alt="" style="float: right"]] # motivation The Radeon X300 seems to have **'two crtc**' interfaces only. And one is always used when the LVDS (laptop builtin display) is enabled (in use). So one is left. Since i use DVI-0 on one workplace and VGA-0 on the other i usually was forced to reset X to make things work, since i wasn't aware of the resource limitation. The error which came up was: % xrandr --auto --output VGA-0 --mode 1024x768 xrandr: cannot find crtc for output VGA-0 The **solution** is easy. Just disable (in this case) DVI-0 output. Next enable VGA-0 output again. % xrandr --output DVI-0 --off % xrandr --auto --output VGA-0 --mode 1280x1024 --right-of LVDS Usability wise this problem is a result of a missing resource counter (maybe it exists) but still the interface 'xrandr' was not very helpful in diagnosing the issue. **I would have expected** an error message as: xrandr: no free crct for output VGA-0 left. you can only enable two devices at a time, maybe disable one to enable the other. lspci shows: # lspci 00:00.0 Host bridge: Intel Corporation Mobile **915GM**/PM/GMS/910GML Express Processor to DRAM Controller (rev 03) 01:00.0 VGA compatible controller: ATI Technologies Inc **M22** [Mobility Radeon **X300**] 00:01.0 PCI bridge: Intel Corporation Mobile **915GM/PM** Express PCI Express Root Port (rev 03) Thanks to [1] # links * [1]