Having two graphics chips in a laptop PC is a great solution if you want high performance sometimes and good battery life the rest of the time. NVIDIA's Optimus technology aims to make this a better experience
Laptops have historically been designed around a balance of performance and portability. Not only do they need to be capable of handling the tasks they are designed for, they need to do so without destroying battery life in the process.
There are always exceptions to this rule. Big, power hungry desktop replacements are almost always designed to be tethered to a power outlet, while more portable laptops often lose out in the graphics department.
Modern graphics chips are usually more complex than CPUs. This adds not only extra power drain but also heat issues. This extra heat is actually the reason why a lot of manufacturers push the term notebook over laptop - having two massively complex chips running all the time means that the form factor is not ideal to use on one's lap.
Trading off between battery and graphical grunt
This has led to a quandary. Integrated graphics hardware is fine for the majority of desktop tasks. It is also a lot less complex, which means it can run at lower clock speeds and generates less heat. Throw on a high definition video, or try and run a 3D game and integrated graphics struggles.
On the flipside, a GPU is overkill for most day to day tasks. Web surfing and PowerPoint presentations aren't graphically intensive, and using a discrete GPU for this just adds extra power and heat drain to a laptop.
There have been many stabs at solutions to this over the years. We have seen discrete GPUs used instead of integrated graphics, but this only exacerbated the problems mentioned above. The industry then moved towards switchable graphics options, where both integrated and discrete graphics were built into the laptop.
One of the major issues with this was that it required users to hit a function key to switch graphics hardware. This would often require a reboot to change displays and, like many more obscure features in computing, sometimes users wouldn't even realise the functionality was there. Or for convenience sake they'd activate the discrete graphics and just run everything on that, thus negating the whole solution.
Even when this technology became driver-switchable it didn't actually improve things. There would be an inherent delay as a laptop changed output from integrated to discrete graphics and while it was a better solution it was still an inelegant one.
Logic dictates that the best solution to this issue would be to just develop a better class of discrete graphics that could run in low power situations. This is a viable path for AMD, which makes both CPUs and GPUs. However for systems using NVIDIA graphics this has been further complicated by Intel's decision to bolt integrated graphics chips onto its CPU packages.
This means that NVIDIA has had to adapt if it wants to keep selling graphics for laptops. This adaptation is known as Optimus technology, and it finally does away with the arbitrary annoyances seen in previous generations of switchable graphics.
The best of both worlds
Basically what NVIDIA has done is put Intel's IGP to work as a display controller. When you are using programs that are graphically undemanding the NVIDIA graphics chip lies dormant. This means you get the benefits of battery life and lower heat most of the time.
|Optimus uses the NVIDIA control panel to oversee its activation. You can set specific per application behaviour or let auto-updated profiles control graphics switching.|
Where the big difference to previous solutions lies is with graphically intensive applications. When NVIDIA's driver detects that the discrete graphics chip is needed it powers up the GPU and uses that to generate the pictures. Unlike previous generations of hardware Optimus laptops don't have a delay or the need for a reboot for this to happen.
When called upon the GPU in an Optimus laptop will fire up and start rendering. It then puts the output images into the IGP's framebuffer. The IGP then outputs this picture on the screen. By using the integrated graphics hardware in this way NVIDIA not only manages to get around the tight integration of the IGP but also manages to power up the discrete graphics hardware without the end user noticing.
This seamless hopping between chips means that Optimus powered laptops will have better battery life than ones using discrete graphics. More importantly though it means that there is much less of a tradeoff between portability and power. You will still chew the battery life if you enter into a mammoth Battlefield 2 session, but you'll be able to finish working and throw on a HD movie without having needlessly burned through your battery life with spreadsheets.
How it works in practice
Of course the promises of this simplicity are grand, but oftentimes the implementation is poor. In order to get more of a picture of how Optimus works, we have been playing with an ASUS N61Jv laptop. This is the first Optimus products to hit the PC Authority Labs, and pairs the Intel HD graphics IGP on the i5-430M CPU with a Nvidia Geforce GT 325M graphics chip.
Fire up a graphically intensive application and the laptop runs it without the soul-crushingly low framerates inherent in Intel integrated graphics. Close the game and the laptop powers down the NVIDIA graphics and the IGP takes over all the display functions again.
|Because the IGP acts as a display controller, the operation of the discrete graphics is transparent to Windows. These Just Cause 2 benchmark results show this in action, with the IGP seemingly punching well above its weight.|
It all just works. Which is the massive advantage brought by this technology. Unlike previous generations of switchable graphics there is absolutely no input required from the end user. Application support comes not only through driver-based autodetection but also through special driver profiles. These profiles are similar to the ones used for SLI support on desktop systems and are automatically downloaded by the NVIDIA control panel app, ensuring ongoing compatibility.
Windows 7 laptops only
This brings to bear an interesting thing to keep in mind when looking at Optimus products. Because of the reliance on the NVIDIA driver to control when the discrete graphics powers up, it is essentially a Windows 7 only technology. Install Linux, Windows XP or Vista and the laptop will only access the Intel HD graphics IGP - the laptop will still output pictures, but you won't have the option of the pretty graphics delivered by the NVIDIA GPU.
This will be a moot point for the vast majority of users, but something worth remembering if you want to diverge from Windows 7.