Intel Z68 Review - The Sandy Bridge Platform Expands

Author: SKYMTL
Date: May 11, 2011
Product Name: Intel Z68 Chipset
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Lucidís Virtu GPU Switching

When it was first announced, NVIDIAís Optimus GPU switching technology was greeted with open arms due to its ability to seamlessly switch between a high performance discrete GPU and the efficient IGP on notebooks. While NVIDIA is busy working on its own switching technology for the desktop market, Lucid has taken a step ahead by introducing Virtu. This is a truly vendor agnostic approach which supports both NVIDIA and AMD cards.

Virtu is very much like Optimus: it utilizes Sandy Bridgeís onboard graphics processor for higher idle efficiency along with media acceleration while leveraging the high performance discrete GPU for gaming and professional workloads. This combination ensures resources are properly designated towards the subsystem that is best suited to handle a given task.

In order to achieve what (in theory) should be a seamless transition between the integrated graphics processor and the discrete GPU, Lucid implements a proprietary software that directs workloads. Basically, there are two options here: the iGPU mode where the main display is plugged into the integrated graphics controller and the dGPU mode

If the software detects a 3D application when in iGPU mode, it will bypass IGP, allow the AMD or NVIDIA card to render and then output the image through the processorís video memory and then towards the motherboardís onboard display connector. This has the potential to cause a performance penalty but as the software matures, any overhead should be gradually reduced. Meanwhile, for 2D loads and media playback / conversion, the information is sent directly through the IGP.

Alternately, if the monitor is plugged into the discrete graphics card through dGPU mode, the benefits of lower idle power consumption will be nullified. This is because the less efficient graphics card will be in charge of 2D and Windows Aero rendering rather than Sandy Bridgeís smaller on-die engine.

Here is Lucid's rundown of the two modes:
  • i-Mode provides users with near zero performance overhead on 3D graphics games, while enjoying Intel Sandy Bridge media features and power saving options when no 3D gaming is used. As this mode allows the added-on VGA cards to stay under idle for most of the system up time, the power consumption is also relatively lower.

  • d-Mode is provided for demanding 3D gamers to achieve 3D performance of discrete GPU installed in the system. In this mode, Virtu allows user to utilize Intel special features such as transcoding, while display is connected to discrete GPU.

Lucidís main control panel is actually quite sparse since all of the action is taking place behind the scenes, hopefully out of the end userís view. This view basically shows whether Virtu is working, which onboard processor is presently handling the workload and the placement of the Virtu logo within applications (along with an option to turn off the logo of course). There is also a performance optimization slider in order to fine tune the image quality in relation to framerates.

The Games tab indicates which games or applications are currently compatible with the virtualization software when in iGPU mode. There are several hundred titles supported and the list has rapidly grown since Virtuís inception. Unfortunately it does tend to take a while until a newly released game is added to the list so itís important to check for updates often.

In dGPU mode, any games supported by the current graphics card driver will work without an issue since virtualization is used for the integrated graphics controllerís functions.

As youíve probably already guessed, there are quite a few loopholes to jump through and on the next page weíll tackle the performance and any issues we encountered when using Virtu.

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