View Full Version : [ubuntu] 11.10 not booting with laptop external monitor connected

November 5th, 2011, 11:26 AM
Hi. I have installed Ubuntu 11.10 (64bit) on a laptop and have an error during boot up if an external monitor is connected. The error occurs just before the Ubuntu boot splash screen would normally be displayed. The error is:

[drm:i9xx_crtc_mode_set] *ERROR* Couldn't find PLL settings for mode!
[drm:drm_crtc_helper_set_config] *ERROR* failed to set mode on [CRTC:4]
(these lines repeated alternately many times)

When boot is stalled at this error I can ctrl-alt-F1 to get terminal log in. A manual start of lightdm gives the above errors again.

The only way I have been able to get to login screen is to disconnect external monitor before switching on the laptop. Once logged in, then I can use external monitor (although setting optimal resolution is a new challenge usually corrected with xrandr –newmode; --addmode etc...).

This problem happens under the following scenarios that I've tested on this laptop only:

USB only trial of Ubuntu 11.10 64bit (not installed on disk)
WUBI install of 11.10 64bit (dual boot with Win 7)
WUBI install of 11.10 32bit (dual boot with Win 7)
Clean install of 11.10 64bit on a separate (extended) partition
Upgrade from 10.04.3 (x64) to 11.10 (x64) on separate (extended) partition

Error does not occur with external monitor connected if grub boot option includes 'nomodeset' however I can't seem to set external monitor resolution with xrandr when I boot with nomodeset option.

I have installed gdm (to use instead of lightdm) and same issue occurs.

Right now I have clean install of 11.10 (x64) on separate partition dual boot with Win7. Does anyone have any idea what I can do about this issue please? Thank you.