Lucidlogix Virtu Makes Hybrid Graphics On
The Desktop Possible
Historically, integrated graphics, with
their notoriously lackluster performance, have been of little interest to power
users. But perceptions began to change with Intel's Sandy Bridge, and later its
Ivy Bridge, microarchitecture. While Sandy Bridge’s DX10-class, Intel HD
2000/3000 graphics engines aren't cutting-edge by any means, they offer enough
performance for many mainstream PC users, and consequently, helped Intel gain
market share in the graphics race. Ivy Bridge further improves the situation
with a more powerful graphics core outfitted with additional execution units
and DX11 support. Whereas Intel's HD 3000 offers 12 EUs, Ivy Bridge's HD 4000
engine has 16.
Intel's
Sandy Bridge
But perhaps the most sought-after feature
of Sandy Bridge and Ivy Bridge is Quick Sync. Quick Sync is a dedicated
encoding/ decoding engine that can burn through video-encoding tasks
lightning-fast. Problem is, Quick Sync is part of the GPU block on Sandy Bridge
and Ivy Bridge processors, and when a discrete GPU is installed and no monitor
is connected to the integrated GPU, Quick Sync is unavailable.
Not being able to use Quick Sync and
discrete graphics simultaneously didn't sit well with enthusiasts, but a
workable solution was made available when LucidLogix introduced Virtu, a
product that can virtualize the GPUs in systems and enabled hybrid graphics
configurations. With Virtu, users can enjoy the benefits of a discrete GPU when
gaming and still leverage an integrated GPU for power savings or Quick Sync.
The best part is that Virtu is supported by a variety of motherboards. On the
following pages we’re going to explain how Virtu works and how you can set it
up on your own system, and then we'll showyou how a hybrid
graphicsconfiguration affected benchmark performance on our test systems.
Lucidlogix Virtu Explained
Although the underlying technology is
relatively complex, it’s somewhat easy to explain and understand how Virtu works.
First and foremost, note that Virtu is a software solution from top to
bottom—save for programming some BIOS code, no modifications are necessary at
the hardware level. Virtu requires special hooks in the BIOS and the presence
of both discrete (dGPU) and processor/integrated (iGPU) graphics in a system,
but that's it.
Lucidlogix
Virtu
When Virtu is installed on a system, it
essentially virtualizes the available GPUs. The name Virtu is actually an
abbreviation of GPU Virtualization. With Virtu, Lucid's Multi-GPU Abstraction
Layer is installed between the OS and drivers, and that abstraction layer
intercepts DirectX API calls from games or applications. At this point in time,
OpenGL and WebGL are not supported. Once a call is intercepted, Virtu’s Rendering
Assignment Manager then analyzes it and decides to shuttle the subsequent task
to either the iGPU or dGPU, based on a set of predetermined application
profiles, which includes hundreds of games and multimedia tools.
Virtu can be configured in two modes:
i-Mode or d-Mode. I-Mode refers to a configuration in which a monitor is
connected to the integrated graphics engine's display output, while d-Mode
means the monitor is connected to the discrete GPU. We mention the modes
available because the final step Virtu performs is dependent on the mode being
used. Once a task is complete, the output (typically a rendered frame) is
copied to the appropriate GPU's frame buffer, where it is finally output to the
screen. When operating in i-Mode, the dGPU’s output is copied to the iGPU’s
frame buffer memory; vice versa for d-Mode.
Currently there are three different
versions of LucidLogix Virtu available to end users: Virtu Green, Virtu
Universal, and Virtu MVP. All the different versions function in a similar
manner, but each has a different feature set. Virtu Green is the most basic
version and works only on Intel platforms. Next up the chain is Virtu
Universal, which works with both Intel and AMD platforms and also adds support
for Lucid’s Virtual V-Sync technology. Finally, there is Virtu MVP, which has
all the features and compatibility of Universal, but adds support for Lucid's
HyperFormance technology, as well.
While they’re independently configurable,
Virtual V-Sync and HyperFormance are interconnected. These two features have
been mistakenly characterized as game performance enhancers, when in fact
they’ll only affect image quality and input responsiveness. Virtual V-Sync
leverages the iGPU’s resources when the discrete GPU is being used to probe the
dGPU’s frame buffer and ensure that only the last fully rendered frame is shown
on the screen. By doing so, Virtual V-Sync prevents tearing artifacts and
always ensures the latest frame data is displayed on screen. It’s only useful,
however, when a game's frame rate exceeds the refresh rate of the attached
monitor, which is usually 60Hz (or 60fps) for mainstream LCDs. HyperFormance
uses a predictive algorithm to ascertain which frames will never be displayed,
and removes any unnecessary rendering tasks for those frames from the pipeline,
freeing up the dGPU to process only the items which will ultimately be
displayed. This results in a decreased workload for the dGPU and an increase in
responsiveness, but like Virtual V-Sync, HyperFormance is only useful when
frame rates exceed the monitor’s refresh rate.
Virtu's Hardware Considerations
Short of having a compatible motherboard,
as well as discrete and integrated processor GPUs, there are no specific
hardware considerations for Virtu. As we’ve mentioned, it’s a software-only
solution. LucidLogix has been working with motherboard manufacturers to have
Virtu included with strategic motherboards—typically those supporting Intel's
Sandy Bridge and Ivy Bridge-based processors—but Virtu is also compatible with
AMD’s A-Series APU chipsets. Due to Virtu’s requirement for both discrete and
integrated graphics processors, however, it does not support any high-end,
enthusiast-class chipsets, like those designed for Intel’s Sandy Bridge-E or
AMD’s Bulldozer, for example, as those processors lack on-die graphics.
Virtu
also supports multimonitor configurations, but multi-GPU support is iffy
At this point in time, Virtu is qualified
to work with single discrete-GPU configurations and is also compatible with any
display output—DVI, Display-
Port, HDMI, etc. are all supported. Virtu
also supports multimonitor configurations, but multi-GPU support is iffy. We
asked Lucid about Virtu’s support for CrossFire or SLI multi-GPU configs and
were told, “The reason for limited support today is our flexibility to plug the
display in i-Mode (to motherboard) or d-Mode (discrete GPU). In i-Mode, which
is the most popular one, we enable additional power savings and noise
reduction, but the vendor control panels for SLI or CrossFire are not
available. Also, the Virtu product line is shipped in mass volumes (expecting
to pass 10 million units by end of year). Virtu is for the mass market. SLI/CF
are relatively smaller markets and require a great deal of work with special
workarounds.” Indeed, when in i-Mode, Nvid-ia's and AMD’s driver control panels
will not load. In fact, if you try to access it when Virtu is enabled in
i-Mode, an error message will pop up saying a supported GPU is not available,
although the drivers for the GPU do load with Windows. The nonfunctioning
control panels prevent users from switching on SLI or CrossFire, though, and
prevent their application profiles from properly detecting games. With that
said, you can start up a system in d-Mode, turn on SLI or CrossFire, then
switch back to i-Mode. but success isn't guaranteed. We did get CrossFire
working in i-Mode. but SLI never scaled properly.
The Competing Standards
Hybrid graphics are hardly new, and
certainly not unique to Virtu. Nvidia and AMD both offer switchable graphics
solutions to achieve many of the same goals as Virtu. Nvidia's Optimus
technology seamlessly switches between discrete and integrated GPUs depending
on an application's needs or available power. AMD’s switchable graphics, while
not quite as seamless as Nvidia's, essentially does the same thing. But both
Nvidia’s and AMD’s technologies are typically relegated to the mobile space,
save for a single Alienware system (the X51) that leverages Optimus.
The
closest Nvidia has come to offering a hybrid graphics solution for desktops is
with this wee Alienware X51 PC.
We reached out to both companies to see if
either had switchable graphics solutions in the works for desktop systems and
got the typical answer that neither company could comment on unreleased
products. Nvidia said there is nothing preventing OEMs from using Optimus on
desktop systems, but that it hasn’t been done because power is much less of a
concern on desktop system, especially since recently released graphics cards
consume little power while idling or sitting at the desktop. A rep for AMD said
something similar: "On desktop platforms, AMD leads in power efficiency
with ZeroCore Power. This vastly reduces power without having to rely on
solutions such as switchable graphics.”
