Video Hardware - Upgrading and Repairing PCs - page 803

• Compute shaders —Provides an additional stage independent of the Direct3D
pipeline that enables general-purpose computing on the graphics processor, part of
Shader Model 5. This feature is supported by processor with integrated graphics.
• Dynamicshaderlinkage —Alimitedruntimeshaderlinkagethatallowsforimproved
shader specialization during application execution.
To obtain a version of DirectX 11 for Windows Vista, see KB971512 at ht-
tp://support.microsoft.com for details.
It's important to realize that DirectX 10/11 GPUs retain full compatibility with DirectX
9.0candearlier DirectX versions,soyoucanplaythelatest gamesaswellasoldfavorites
with a DX10 or DX11-compliant video card. Updates for DirectX are provided via
www.windowsupdate.com . More information about DirectX is available from Microsoft
at www.microsoft.com/directx .
Dual-GPU Scene Rendering
In Table 12.16 , Iplaced thedevelopment ofdualPCIe graphics cardsolutions astheninth
generation of 3D acceleration. The ability to connect two cards to render a single display
more quickly isn't exactly new: The long-defunct 3dfx Voodoo 2 offered an option called
scan-line interfacing (SLI) that pairs two Voodoo 2 cards on the PCI bus, with each card
writing half the screen in alternating lines. With 3dfx's version of SLI, card number one
wrote the odd-numbered screen lines (one, three, five, and so on), whereas card number
two wrote the even-numbered screen lines (two, four, six, and so on). Although effective,
use of SLI with Voodoo 2 was an expensive proposition that only a handful of deep-pock-
eted gamers took advantage of.
A few companies also experimented with using multiple GPUs on a single card to gain a
similar performance advantage, but these cards never became popular. However, the idea
of doubling graphics performance via multiple video cards has proven too good to aban-
don entirely, even after 3dfx went out of business.
NVIDIA SLI
When NVIDIA bought what was left of 3dfx, it inherited the SLI trademark and, in
mid-2004, reintroduced the concept of using two cards to render a screen under the same
acronym. However, NVIDIA's version of SLI has a different meaning and much more in-
telligence behind it.
NVIDIA uses the term SLI to refer to scalable link interface. The scaling refers to load-
balancing, which adjusts how much of the work each card performs to render a particular
scene, depending on how complex the scene is. To enable SLI, you need the following
components: