Asus Eee PC 1215N 12in netbook

Optimus on board

The 1215N's performance comes from its dual-core Atom CPU and from its second-generation Nvidia Ion integrated chipset. It's the built-in GPU that powers the 1366 x 768 screen and HDMI port, but the graphics core integrated into Intel's CPU is put to use too.

Optimus operates on an app-by-app basis - select which GPU in the contextual menu or the control panel's list of pre-sets

Asus has implemented Nvidia's Optimus technology, which keeps the discrete GPU powered down until it's really needed. The GMA 3150 handles the screen full-time, and rather than switch from one to the other, with the inevitable screen flicker that goes with it, Optimus cleverly gets the Ion GPU to write directly into the 3150's video buffer.

In that respect, the Ion operates more as co-processor than a graphics controller. The switch is transparent, to the extent that you're left wondering whether it has happened at all. Some kind of taskbar icon showing which GPU is in play would be nice, Nvidia.

Nvidia's software chooses whether to enable the Ion based on a list of apps that can use it. You can specify which GPU a given app will prefer by tweaking the settings in the Control Panel, or by selecting an entry from the contextual menu.