Intel KMS vs. UMS With Ubuntu 10.04

[Xake]

Users whose TV out is broken are not going to say to themselves 'Oh, maybe I should hack around with /etc/X11/xorg.conf and see if UMS option will make my TV work...'; They are just going to not use TV out.

But for us who NEED TV-out it IS an option. For me I stumble over it while debugging (all on my own, mind you, as I have filed a bugreport, but noone in the intel team seems to want to help (possibly because it is a hell to debug this kind of things without be able to have hands-on time with a failing computer)) and I *AM* very happy that UMS is an option for me.

[MrCooper]

Last week we published benchmarks looking at the ATI Radeon KMS vs. UMS performance and found the user-space mode-setting support with the ATI driver (that is also limited to using DRI1 with these older code-paths) [...]

That's exactly why there's less difference with the Intel drivers: they're still using GEM/DRI2 with UMS.

[chetancrasta]

Kernel mode-setting support can be toggled at boot-time by adding i915.modeset=0 to the GRUB kernel boot line to boot with the user-space mode-setting support

Kernel mode-setting can be disabled by adding nomodeset to the Grub kernel boot line.

I had to disable kernel mode-setting on my i965 Intel Mobile GM965/GL960 because it did weird things with a panning desktop and I couldn't adjust screen brightness in Ubuntu Lucid Lynx.

Disabling kms with nomodeset fixed these problems.