Enable Quartz Extreme and Quartz 2D Extreme
Quartz Extreme and Quartz 2D Extreme mainly makes use of the Vertex and Pixel shaders found on the NVIDIA® GeForce Go 7300 Graphics card to offload some CPU Calculations, so the CPU can focus on decoding movies and process network packets. It also enables users to play games on their AppleTV.
Quartz Extreme should already be enabled by default. You can enable Quartz 2D Extreme & Quartz Extreme without installing anything by typing the following from the command line.
sudo defaults write /Library/Preferences/com.apple.windowserver Quartz2DExtremeEnabled 1
defaults write /Library/Preferences/com.apple.windowserver GLCompositor -dict tileHeight -int 256 tileWidth -int 256
You can also use the following to get it enabled
First of all you need to get Apple's Quartz Debug. You can get it from Apple's XCode or Developers Tool or from here 
Copy it to your AppleTV. Then Run Quartz Debug. Go To Tools --> Enable Quartz Extreme and then go to Tools again, this time select Enable Quartz 2D Extreme. Quit AppleTV and voilà you have Quartz Extreme and Quartz 2D Extreme enabled!