Lucid Virtu Graphics Technology

Lucid (formerly LucidLogix) appeared on the enthusiast horizon with their "Hydra" technology, which purported to enable vendor-agnostic multi-GPU systems. Users would be able to combine the performance of different video cards from different vendors, rather than being constrained to the cards required by ATI CrossFireX or NVIDIA SLI. Hydra didn't work as well as had been hoped, but the introduction of Intel's new Z68 chipset came with an announcement that Intel had licensed Lucid's "Virtu" GPU virtualization technology. This brings significant new features to Z68 motherboards, and Benchmark Reviews will examine them in this article.

One of the first Z68 Express-based motherboards available is ASUS' P8Z68-V Pro, which is the motherboard I'll be using to examine Virtu. While the Z68 Express chipset enables the simultaneous use of both the integrated GPU (iGPU) of Sandy Bridge processors as well as a separate graphics card or cards, all you can do with this capability is run multiple monitors; Virtu gives you more options. Specifically, Virtu supports two different modes:

• Virtu i-Mode allows seamless switching between integrated Intel HD graphics and a separate graphics card, resulting in significant power savings when the power of the graphics card isn't required. In this mode the monitor is plugged into one of the motherboard's video ports.
• Virtu d-Mode enables the use of a separate graphics card while allowing the use of Intel's "Quick Sync" video transcoding technology, which runs on the iGPU. In this mode the monitor must be plugged into the graphics card.

Virtu's basic "trick" is to keep active a video source- the motherboard video or video card- that would normally be disabled since no monitor is connected to it. Once this is done, Virtu can do things like selectively power down video sources that aren't being used, copy the frame buffer contents from a video card to the iGPU's video buffer, and enable the use of iGPU computation.

Virtu's i-Mode supports only a single, single-GPU graphics card, while d-Mode supports multi-GPU graphics cards as well as CrossFireX and NVIDIA SLI configurations. Lucid claims the Virtu technology will work equally well with video cards from NVIDIA or AMD. NVIDIA's forthcoming Synergy technology, which ASUS will supply via an update to P8Z68 motherboard owners, will only work with NVIDIA graphics cards.

If you plan to use a video card with your Z68-based computer, there are three possible ways you can configure your system:

1. Native video card only, with iGPU multi-monitor support disabled. The iGPU is inactive just as it would be in a P67-based motherboard.
2. Virtu i-Mode, with your monitor plugged into a motherboard video port.
3. Virtu d-Mode, with your monitor plugged into the video card.

For Virtu to work, you must enable the "iGPU Multi-Monitor" setting in the P8Z68's UEFI BIOS, even if you're going to use only one monitor. For i-Mode, the "Initiate Graphic Adapter" selection must be set to "iGPU"; for d-Mode, it must be set to "PCIE/PCI". Note that if you decide to switch from one mode to the other, you must change the setting in the UEFI before switching the video cable to the other connector; otherwise, you'll get a black screen when you boot. The image below shows the correct UEFI BIOS settings for i-Mode (top) and d-Mode (bottom). In both cases, iGPU Multi Monitor must be enabled; for i-Mode, the iGPU must be set to initialize first, whereas for d-Mode, PCIE/PCI must be set to initialize first. While these settings are specific to the ASUS P8Z68-V Pro motherboard I used for this article, they should be similar on other Z68 Express-based motherboards.

Lucid supplies a simple control panel application for Windows, shown below. The large green button at the upper left lets you disable iGPU graphics in d-Mode, and discrete GPU graphics in i-Mode; you can also choose to have a "Virtu" label appear either permanently or for a few seconds in a designated screen corner to let you know that Virtu is active in the running application.

Unlike NVIDIA's Synergy technology, which will switch between integrated and discrete graphics automatically depending on the load, Virtu must be told which applications you want it to be enabled for. You do this in the "Games" tab in the Virtu control panel, which comes pre-populated with a list of games. To add a new game, simply click the "Add" button and browse to the location of the game's executable file. This worked well to add games, but I couldn't get it to work for adding some benchmark programs. Adding the Street Fighter IV benchmark was easy, but although I added the executables for the SPECViewPerf and SPECapc Lightwave benchmarks I used in my review of the ASUS P8Z68-V Pro motherboard, Virtu would not "engage" for these benchmarks, relegating them to running under Intel HD Graphics. This may have something to do with the modular nature of these benchmarks, but be aware that it's possible some of your games might not be able to take advantage of Virtu. It's a good idea to enable the on-screen "Virtu" label when you're adding applications to this list so you'll know if it's working when you try the app for the first time.

When running in i-Mode, your monitor's video cable is connected to the motherboard video port rather than the video card. While Virtu manages to enable the video card's driver anyway, the NVIDIA and AMD control panels won't be available in this mode (in fact, you'll get an error message from these control panels every time you boot Windows, which is annoying), limiting you to in-game graphics settings.

Virtu Test Methodology

To discern the performance and power characteristics of each Virtu mode as compared to a "native" graphics card, I chose an AMD Radeon 6850 as the graphics card and tested the following applications:

• Unigine Heaven 2.1 Benchmark
• Street Fighter IV Benchmark
• Crysis Warhead
• Battlefield: Bad Company 2

I ran each test against the native Radeon 6850, Virtu i-Mode (which should use the Radeon 6850 automatically, since each game was in the Virtu Games list), and Virtu d-Mode. Each test was run at 1680x1050 as well as 1920x1200 resolutions. Virtu i-Mode is the most interesting case since it must somehow copy the frame buffer contents from the Radeon 6850 to the iGPU's frame buffer, which I would expect to incur a performance penalty...but we'll see.

Lucid Virtu Test Results

Unigine Heaven 2.1

The Unigine Heaven 2.1 benchmark is a free publicly available tool that grants the power to unleash the graphics capabilities in DirectX-11 for Windows 7 or updated Vista operating systems. It reveals the enchanting magic of floating islands with a tiny village hidden in the cloudy skies. With the interactive mode, you can explore the intricate world presented. Through its advanced renderer, Unigine is one of the first applications to showcase the tessellation features of DX11-capable graphics cards, exhibiting the possibilities of enriching 3D gaming.

Here we see a pattern that will be repeated throughout our tests: the performance of Virtu d-Mode matches that of the native 6850, and there's a small (1fps in this case) penalty for running with Virtu i-Mode.

Street Fighter IV Benchmark

Street Fighter IV uses a new, built-from-scratch graphics engine that enables CAPCOM to tune the visuals and performance to fit the needs of the game, as well as run well on lower-end hardware. Although the engine is based on DX9 capabilities, it does add soft shadows, High Dynamic Range lighting, depth of field effects, and motion blur to enhance the game experience.

The game is multi-threaded, with rendering, audio, and file I/O all running in different threads. The development team has also worked to maintain a relatively constant CPU load in all parts of the game so that on-screen performance does not change dramatically in different game scenarios.

Again we see no penalty for using Virtu d-Mode, although there's a 7fps and 10fps penalty at the test resolutions for running in Virtu i-Mode.

Crysis Warhead

Crysis Warhead is an expansion pack based on the original Crysis video game. Crysis Warhead is based in the future, where an ancient alien spacecraft has been discovered beneath the Earth on an island east of the Philippines. The game uses a refined version of the CryENGINE2 graphics engine. Like the original Crysis, Warhead uses the Microsoft Direct3D 10 (DirectX-10) API for graphics rendering.

Benchmark Reviews uses the HOC Crysis Warhead benchmark tool to test and measure graphic performance using the Airfield 1 demo scene. This short test places a high amount of stress on a graphics card because of detailed terrain and textures, but also for the test settings used. Using the DirectX-10 test with Very High Quality settings, the Airfield 1 demo scene is configured with 4x anti-aliasing and 16x anisotropic filtering to create maximum graphic load.

Although introduced in 2008, Crysis Warhead still serves as a test of the most powerful graphics cards. It's impressive to see that d-Mode is as fast as the native 6850, and that i-Mode has only a small 1fps penalty.

Battlefield: Bad Company 2

The Battlefield franchise has been known to demand a lot from PC graphics hardware. DICE (Digital Illusions CE) has incorporated their Frostbite-1.5 game engine with Destruction-2.0 feature set, which allows destructible environments, with Battlefield: Bad Company 2, and adds gravitational bullet drop effects for projectiles shot from weapons at a long distance. The Frostbite-1.5 game engine used on Battlefield: Bad Company 2 consists of DirectX-10 primary graphics, with improved performance and softened dynamic shadows added for DirectX-11 users.

In our benchmark tests of Battlefield: Bad Company 2, the first three minutes of action in the single-player raft night scene are captured with FRAPS.

And again, d-Mode equals native performance, and i-Mode takes a small hit.

Virtu Performance Penalty

In my testing, Virtu's d-Mode imposes no performance penalty, while i-Mode generally had a minimal performance penalty. This is impressive since in i-Mode, Virtu's driver must be copying each frame from the frame buffer on the Radeon 6850 video card to the frame buffer used by the iGPU. Here are the statistics for i-Mode performance penalties for these tests at 1920x1200:

As you can see the performance penalty for using Virtu's i-Mode is quite small, certainly smaller than I would have expected. In the low-frame-rate cases where the performance difference is most important (Heaven and Crysis Warhead), there's only a 1FPS penalty, which won't be noticeable. This makes sense when you think about it: Virtu's driver can obviously handle some hundreds of 1920x1200 frames every second (as indicated by the Street Fighter IV results), so low-frame rate games won't be constrained by this mechanism, and thus exhibit minimal performance differences.

Virtu Power Saving

The point behind Virtu's i-Mode is to save power by using the integrated GPU when the performance of a discrete graphics card is not required. To test this, I measured system power consumption (not including the monitor) at the Windows login screen, playing back a full-screen MP4 file, and running the Street Fighter IV benchmark.

This is a classic case of "Your mileage may vary." Obviously, the power savings of Virtu will depend largely on the video card you have. As expected, using the native Sandy Bridge GPU is the lowest power option. Virtu d-Mode saves no power at all over the native 6850, while we see a significant 21-watt savings using Virtu i-Mode when playing the full-screen MP4, since Virtu doesn't fire up the Radeon 6850 to do this, and the card stays in idle mode, using only about 20 watts of power, which is the idle power Benchmark Reviews has measured for Radeon 6850s in separate reviews. The power savings with larger, more power-hungry graphics cards would be even larger.

It's a little disappointing to see that Virtu d-Mode saves no power (the 2 watt difference between d-Mode and the native 6850 in MP4 playback is within the margin of error for these measurements), but that's not what it's designed for. Given that the performance penalty for using i-Mode is quite small at only about 5%, using i-Mode is the obvious choice if you're using a single, single-GPU graphics card. The only reason to use Virtu d-Mode is if you want to use Intel's Quick Sync iGPU transcoding, or have a multi-GPU card or multiple graphics cards that require d-Mode.

Virtu Final Thoughts and Conclusion

Virtu isn't perfect: you must manually designate the programs you want it to work with, and as I discovered, not all programs will work (there's probably a reason that program listing tab in the Virtu control applications is labeled "Games").

The architecture of the system also makes switching between i-Mode and d-Mode clumsy: you must reboot your system and change the "Initiate Graphics Adapter" setting in the EUFI BIOS to select either "iGPU" (for i-Mode) or "PCIE/PCI" for d-Mode. You then reboot again and switch the video cable to the appropriate output: if you forget to switch the video cable, or switch it without making the change in the BIOS, all you'll see is a black screen. Still, most people will pick a mode and stick to it, so this probably won't be a problem in the real world.

While Lucid Virtu technology still has a few rough edges, it has the advantage of working with both AMD and NVIDIA video cards, while NVIDIA Synergy will be functional only with NVIDIA video cards. But based on the way NVIDIA Optimus technology works on existing laptop computers, it may well be easier to use, without the application problems I saw with Virtu. ASUS says they'll supply Synergy as a free update for Z68 Express motherboard owners when it's available. Still, since Synergy's not available yet, it may have other issues and limitations that Virtu doesn't, and we don't yet know how its performance and power savings will compare.

For now, Virtu's the only game in town, and within its few limitations it works very well. Virtu is a compelling reason to prefer Z68 Express motherboard over a P67 Express motherboard.

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