Nvidia's Optimus Transforms the Laptop PC

The war between battery life and performance has been going on for as long as we've had notebook computers. Both are important factors in any mobile design, and the most oft-asked questions of any prospective buyer. Both figure into the equation, but there has to be a balance. No matter how fast a laptop is, brief battery life can quickly turn it into a pseudo-desktop that is always tethered to the nearest power outlet. The opposite is also true; many netbooks offer excellent battery life, but their performance leaves much to be desired.

Individual components also try to find the happy medium between power and performance. Mobile processors have done their job by offering significant power savings through lower core speeds and voltages, enhanced sleep states, and even the ability to shut down unused cores. Other basic power-saving strategies involve shutting off idle components such as hard drives or WiFi radios. But the graphics core remains an area of contention.

Power users want the speed, features, and flexibility of a dedicated graphics processing unit, but apart from high-end gaming notebooks, discrete GPUs' higher power requirements and heat production have slowed adoption levels, especially with smaller-form-factor tablets or netbooks. Base-level integrated graphics platforms, by contrast, can be great power-misers, but their performance levels come nowhere near that of a discrete solution. The most logical solution would be to offer both and switch between the two, which is where Nvidia's new Optimus technology comes in.

Switchable or hybrid graphics are nothing new. The technology started out with physical hardware switches to change GPUs, but was very complex from a design point of view. The system needed to be rebooted in order to switch GPUs, so most users didn't even bother with it.

Nvidia then launched a second iteration, while ATI introduced its Switchable Graphics Technology, both of which allowed for a software switch -- with a nominal delay of five to 10 seconds -- between the IGP graphics and the discrete graphics core. No more reboots was a big improvement compared to hardware switching, but this still required users to switch graphics manually, and some applications even blocked the GPU change. When you add in complex driver code, this clearly wasn't quite ready for prime time.

Optimus Primed

With the Optimus technology unveiled last month, Nvidia has taken the laundry list of user complaints and cleared virtually all of them off the board. Optimus operates a lot like a hybrid car, which enhances fuel economy by dynamically shifting between gas and electric power. Instead of different types of fuel, an Optimus notebook will switch between integrated and discrete graphics on the fly, saving power and adding flexibility.

Instead of forcing the user to initiate the graphics switch, Optimus does it automatically, with software drivers choosing the appropriate GPU for each application: Basic office tasks get the integrated graphics, while firing up a graphically intense application such as a game or video playback triggers the discrete GPU. This switch happens very quickly, and in fewer steps, taking approximately 200 milliseconds to move from one GPU to the other.

Another improvement of Optimus technology is that even when the discrete GPU is rendering, the default display output is still the IGP. Rather than using system memory, the Optimus Copy Engine transfers data from the GPU, across the PCI Express bus, and into the frame buffer of the IGP, all without affecting performance. This provides consistency for the LCD display and eliminates any screen flicker associated with a hardware switch between two different GPUs. It also allows the discrete GPU, and the associated PCIe lanes, to be powered off without any change to the IGP display output.

The ability to switch graphics dynamically and instantaneously is the major improvement of Optimus technology, and without needing any manual intervention to switch, the user can concentrate on the task, rather than trying to figure out which GPU is in use. In fact, with no delay or screen flicker, the entire process should be fully transparent to the end user.

But a lot of this still depends on the quality of the software and drivers. In theory, the Nvidia driver would first analyze the program being launched, then activate the GPU that is best suited for that particular task. It does so using the Optimus Routing Layer, which recognizes various graphics calls such as DirectX, DirectX video acceleration, and CUDA, and then allocates the hardware resources appropriately.

The second part is the Optimus Profile, which are settings for each application detailing the features, if any, that can benefit from a discrete GPU. Users can add profiles, update existing ones, and even choose to have new profiles downloaded automatically.

Optimus does use standard Microsoft APIs and transfers the discreet GPU data over the PCI Express bus, so there is no need for complex, multi-product driver sets. Costs are also lower and designs less complicated compared to older switchable graphics solutions, as there is no need for expensive multiplexers or other proprietary hardware. Windows 7 helps the graphics switching transition, as it fully supports two independent graphics processors and driver sets, and moves away from the limitations of Vista.

Optimus technology is also very flexible and can be used in systems ranging from diminutive netbooks all the way up to behemoth multimedia laptops. The overall benefits and features will remain the same, and all that will really change is the performance level of the GPU.

The Wave of the Future

As notebooks have continued to supplant the traditional desktop in both home and business environments, a technology like Nvidia's Optimus seems finally ready to take that final step to mass market acceptance. The incredible growth of mobile computing has led users to demand a desktop-like environment, only in a smaller form factor.

Buyers don't want to be told that the latest and greatest notebook will have trouble displaying a 1080p video or playing World of Warcraft, or that battery life will be a meager two hours at best. People are not just adding a new notebook, they are replacing a desktop.

Given the choice, mobile users want a dedicated GPU, and the more powerful the better. Images are crisper, video is faster, and games no longer look like a slideshow. The caveat has always been the extreme toll this takes on battery life, which is not an adequate trade-off for many. If Optimus can get rid of this last hurdle, and with ease of use and style, discrete mobile graphics are due for a renaissance.