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Review: NVIDIA Optimus technology: mobile GPU implementation done right?

by Tarinder Sandhu on 9 February 2010, 14:00


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Switchable Graphics: why fix something that ain't broke?

The problem. Why fix something that ain't broke?

The basic rule of buying hardware is that the more you spend, the better the specification. Spend £300 on a mainstream laptop and the chances are that, at its heart, it will have a basic CPU and integrated graphics. Both are fine for everyday tasks, and it's no wonder that these kinds of laptops sell by the proverbial shedload.

Increase the budget to £500 and you will receive a better class of CPU and, most likely, a dedicated graphics card that'll be significantly faster than the integrated graphics (IGP) for playing games. Our reviews highlight this in no uncertain terms. By dint of their sheer processing power, discrete mobile graphics also make a case for running an ever-growing number of applications on the GPU instead of the CPU: video transcoding and photo-editing being two obvious examples. So all good, then?

But how to conserve the battery

The inherent problem of discrete GPUs is that, despite the best efforts of AMD and NVIDIA, the latest generation of mobile GPUs (mGPUs) consume considerable juice, even when in supposedly idle mode. Power-draw credentials aren't a problem when plugged into the mains, naturally, but do rear their ugly head when the laptop's run from the built-in battery. Play games whilst the laptop is powered from the battery and the effective mobile-life is shortened by 50 per cent, or more.

NVIDIA/ATI and the laptop manufacturers have implemented various technologies to combat the noisome effects of constant mGPU usage on battery-life. Appreciating that the mains-free laptop's power-draw characteristics of mGPUs will never match those of integrated graphics, the culmination of NVIDIA's approach currently lies with Switchable Graphics, released in 2007.

Switchable Graphics - a half-baked solution?

As the name suggests, Switchable Graphics enables a laptop to flit between the power-frugal IGP for basic 2D work and the mGPU for the heavy lifting required for 3D gaming and GPU-accelerated applications. First brought to market by Sony (with a physical switch on the SZ range) and now evolved such that a system reboot isn't required, Switchable Graphics appears to be the panacea for those looking for incredible battery-life, made possible by IGPs, and truly mobile 3D performance, availed by mGPUs - all through a one-touch system.

Indeed, the latest ASUS laptops can switch between the mGPU and IGP in a matter of seconds, with behind-the-scenes trickery either enabling or disabling the mGPU and driver. We agree with NVIDIA that the actual process is slightly cumbersome and that it requires at least a basic knowledge of what's going on, as there's little on-screen notification to inform the user if the laptop's in IGP or battery-sapping mGPU 'mode'. The user needs to manually select the mGPU if playing a game - or have it down by some automated system: ASUS Power4Gear - and then remember to turn it back off, via the system-tray icon, when running Word, if battery-life is important.

Leading on from the above, NVIDIA reckons that, in a battery-powered environment, a fully automated and seamless system of IGP/mGPU switching makes implicit sense - the laptop needs to call the relatively power-hungry mGPU into action only when it's required, reverting back to the IGP the very second the GPU-heavy task is accomplished. This, in a large nutshell, is what Optimus tries to do.