Nouveau is an open source graphic driver for nVidia cards.
Install the following packages :
pacman -S nouveau-drm xf86-video-nouveau
You can use the following xorg.conf, which allows you to easily switch back to other drivers :
Section "Device" Identifier "nvidia" Driver "nouveau" #Driver "nv" #Driver "nvidia" EndSection
Note from the Featurematrix for NV50 chipset and Xv support :
Now it works fine, but you need Xserver from git. In other case you need to run a composite manager (Compiz won't work, something like xcompmgr or KWin with XRender).
So you can set up xcompmgr.
1) Add the following line to /etc/modprobe.d/modprobe.conf:
options nouveau modeset=1
2) Remove all "vga=" and "video=" options from your kernel commandline in /boot/grub/menu.lst
You can have a look at Intel instructions for an early start Intel_Graphics#KMS_.28Kernel_Mode_Setting.29
If this still does not work, you can try the way recommended by upstream, which is to install a kernel already including the nouveau drm modules : kernel26-nouveau-git
3D support is still very experimental and unsupported, but if you want to give it a try anyway, you can install nouveau-dri-git.