Information on the nVidia Optimus technology

After exploring the Optimus system settings on my Asus U31JG I've decided to share what I've learned here. Since I did not find any other Optimus-specific thread on the forum I went ahead and created this one. This post will tell you where and how you can access the Optimus settings, and how you can use them to, at least crudely, optimize performance vs. battery life on an Optimus-enabled laptop. The amount of settings available is unfortunately very limited, but hopefully future drivers will implement more. Feel free to comment and ask questions about Optimus in the thread, hopefully we can get a discussion going where people can contribute whichever information they have on this exciting feature.

Acronyms used in this post:
IGP = Integrated Graphics Processor
dGPU = dedicated Graphics Processing Unit (the dedicated nvidia graphics processor)

Optimus settings
The Optimus settings are accessed through the Nvidia Control Panel. (It is worth noting however that you can specify if a program should be run by dGPU or IGP both permanently and on a one-time basis through right clicking the shortcut or program file). In the Nvidia Control Panel under Manage 3D settings it's possible to set your Preferred graphics processor to either Auto-select, High-performance NVIDIA processor or Integrated graphics. Auto-select will let the Optimus system automatically choose whether to use the dGPU or the IGP according to one of two things; calls or profiles. The calls are types of graphics output that trigger the use of the dGPU, according to the Optimus white paper (page 16) these include 3D game engines, DirectX applications, video playback and CUDA applications. The profiles are either automatically downloaded from nvidia or defined by the user and can be found under the tab Program Settings. These will simply let the Optimus system know which graphics processor to use when a specific program is run. Choosing Integrated graphics as Preferred graphics processor appears to disable the choosing of the dGPU by use of calls, although the profile settings still override this. Setting the Preferred graphics processor to High-performance NVIDIA processor does not however mean that the IGP will be disabled or even idle. It seems that the only thing this choice does is make the programs who's profiles are set to Use global setting use the dGPU. According to the Optimus whitepaper (page 14, note that the whitepaper uses GPU as the term for the dedicated nvidia graphics processor);

which means that even when the dGPU is used for graphics processing the IGP is still active, as the frames are actually still being rendered to the screen by the IGP.

You can enable an activity monitor for the dedicated nvidia card through the Display GPU Activity Icon in Notification Area option under the Desktop menu item to check if the dGPU is being used or not. This can be helpful when fiddling around trying to find out how Optimus works.


Conclusions
The settings that are available in the current driver version (267.76) give us some control over the Optimus functionality, however what I would really like to see implemented in future driver versions is the possibility to let these choices be set according to whether the laptop is running on battery or is plugged in, so that you won't have to go into the control panel and change it whenever you want more or less power usage.

It is especially worth noting that according to the Optimus whitepaper (page 16) the following call types trigger the activation of the dGPU:

This means that if you fire up casual DirectX games or want to watch a video while on battery, things that the IGP should be able to handle easily, the power drainage will be a lot higher than necessary due to the dGPU being triggered. While being plugged in this doesn't really matter, but while on battery it does. Thus I would recommend those who use an Optimus-capable laptop for watching videos and playing casual DirectX games while on battery power to either select the IGP as the Preferred graphics processor while on the go, or to configure specific profiles for the applications in question. It should help save power and reduce noise and heat.

Sources:
Optimus Technology
http://www.nvidia.com/object/LO_opti...itepapers.html

 

Links with information on Optimus:
Nvidia Optimus - Wikipedia, the free encyclopedia
NVIDIA Optimus - Truly Seamless Switchable Graphics and ASUS UL50Vf - AnandTech :: Your Source for Hardware Analysis and News
Nvidia Optimus Review - Notebookcheck.net Reviews
NVIDIA Optimus automates graphics switching, promises the best of both worlds -- Engadget

 

I've been meaning to look up this information for my Thinkpad T410s but hadn't gotten around to it. Thank you!

 

Thanks for the thread, I've added it to the Gaming Forum Information Booth!