I'm new to the forums, having just bought a 6850 yesterday to replace my GTX 280, which died (again).
An introduction (skip to the tl;dr below if you only care about the technical stuff)
I am a avid Linux user and a huge believer/supporter of/in open source. I had said for years that I would switch to the first vendor who released the specs or code for a high quality graphics chip. I was excited when ATI did it, and have been following it for quite some time.
I have been an Nvidia customer since they bought out the Voodoo card tech way back when. When no vendors were truly supporting Linux 3D acceleration in an OSS manner, they continued to be my choice as their Linux drivers do work quite well. Recently, however, I have had several bad experiences with hardware from them. Manufacturing defects in the 8000 series, and now discovering many of the 280 chips are lemons (I've had 2 die, and Nvidias forums confirm I'm not the only one). Then I read the 400s turn your computer into an easy-bake oven, I decided it was time to give ATI a shot.
As I said, NV's Linux drivers work well, and setup is truly a breeze. However, I don't care if it's easy - if I can make this ATI card do what I need, I will be grateful. So far, I've had some success, and a bunch of failure. I'm typing this using the card, so at least I'm making progress.
TL;DR: The tech part
My goal: Dual head setup, xinerama. KDE4 with composite effects. Run a few games in Wine (Mostly Eve Online). Smooth animations on the desktop.
Current situation: I can get composite or xinerama, not both. With xinerama on, the second monitor goes to a weird pattern during boot, then corrects and is usable. KDE reports I can not turn desktop effects on because XComposite and XDamage are not available. I do have 3D acceleration in both cases. Scrolling windows is choppy.
1) Is my goal attainable using the OSS drivers at this point? If not, I am ok using catalyst until they are more stable/feature complete.
2) Assuming the answer to 1 is no, how do I configure the card to use both xinerama and composite with the fglrx driver?
3) Why would my second monitor be all "garbage" during boot, then correct?
4) What is UseFastTLS? I've seen posts saying to set it to everything under the sun, and none explaining why or what it is. Even Google didn't help!
5) Should my xorg log be showing dri failed to load?
That should give me a starting point. Apologies for the wall of text, and much thanks for any assistance.
As for the open source driver; why not try it? I use the open source driver, but I do not use compositing (running a bare bones Openbox setup) so I cannot report on its effectiveness here. (You should be able to use xrandr in exactly the same way with Catalyst and with xf86-video-ati. However, you may need to increase the virtual screen size with Catalyst, since it requires that kernel mode-setting be disabled. Instructions are provided in the thinkwiki article I linked to above.)
Wow! You just solved a whole lot of problems in one shot! Do you drink beer? I'll send you a case...
Beer is good :-) (Fortunately for you, I like cheap beer.)
And yeah, multi-monitors is not an easy affair on Linux. There are a lot of pitfalls, and they differ depending upon your driver. I'm in the (very long) process of writing my own window manager geared towards multi-monitor setups, so I need to be in "the know" :-)