I'm trying to get 3D going with a HD3870 using radeonhd with the driver, drm modules and mesa built from git sources following the xorg wiki instructions. I'm on Gentoo using kernel 2.6.30.

I have a dual screen setup and when I first tried to get 3D working and couldn't I just shrugged it off as having done something wrong and thought I'd try again some time in the future.. but then I was messing around with my xorg config and managed to break my uber cool randr dual screen setup and behold, 3D was suddenly working - until I fixed my xorg conf to get rid of the awful clone mode.

So.. is it supposed to work when I have two monitors set up using randr and if yes where to start looking for the problem..

In KDE 4.2 when I enable desktop effects, I get kicked back to kdm. I log back on and desktop effects is enabled in the menus but isn't working. Using just one monitor or clone mode, it works (with corruption but still). Google Earth just shows pitch black where the sweet 3D action should be.

Glxgears, however, works just fine.

Mesa: CPU vendor: AuthenticAMD
Mesa: CPU name: AMD Processor model unknown
Mesa: Mesa 7.6-devel DEBUG build Aug 20 2009 19:18:55
Mesa warning: couldn't open libtxc_dxtn.so, software DXTn compression/decompression unavailable
IRQ's not enabled, falling back to busy waits: 2 16
Mesa: MMX cpu detected.
Mesa: 3DNow! cpu detected.
Mesa: SSE cpu detected.
Mesa: Not testing OS support for SSE, leaving enabled.
no rrb
9054 frames in 5.0 seconds = 1810.728 FPS
9112 frames in 5.0 seconds = 1822.372 FPS
I've always sucked at making a xorg config file so most likely I just messed it up somehow.. here it is:

Section "Monitor"
        Identifier   "BenQ"
        Option       "PreferredMode" "1920x1080"

Section "Monitor"
        Identifier   "Acer"
        Option       "RightOf" "BenQ"
        Option       "PreferredMode" "1280x1024"

Section "Device"
        Identifier  "3870"
        Driver      "radeonhd"
        Option      "monitor-DVI-I_1/digital" "BenQ"
        Option      "monitor-DVI-I_2/digital" "Acer"
        Option      "RROutputOrder" "BenQ"
        Option      "AccelMethod" "exa"
        Option      "DRI" "on"

Section "Screen"
        Identifier "MyScreen"
        Device     "3870"
        DefaultDepth     24
        SubSection "Display"
                Depth     24

Section "DRI"
        Mode    0666
My xorg log can be found at http://pastebin.com/m533b2de7 and glxinfo at http://pastebin.com/df7e431a

any other information and/or logs you want to see, ask and I shall try to provide..