|Lucid Virtu Graphics Virtualization Technology|
|Reviews - Featured Reviews: Video Cards|
|Written by David Ramsey|
|Wednesday, 11 May 2011|
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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'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:
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:
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.