Cyrix, Centuar support AMD's 3D
May 04, 1998, TechWeb News
Title developers divided over relative merits of the latest
crop of techniques and features -- CPUs, graphics chips
ante up for PC games
By Anthony Cataldo And Rick Boyd-merritt
Long Beach, Calif. - The struggle to define the next level of PC graphics will
come into high relief as the Computer Game Developers Conference opens
here this week. The outcome of a battle of seemingly arcane features and
techniques may determine the fates of controller and processor vendors-and
boost the PC's capabilities in the process.
S3 Inc. will make a long-overdue return to the high-end 3-D graphics market
with its introduction of the Savage 3-D. The graphics accelerator will confront
some stiff competition, including Nvidia Corp.'s Riva TNT and 3Dfx
Interactive Inc.'s Banshee. Meanwhile, Intel Corp. and its rivals will pitch
floating-point instruction extensions aimed at enhancing their CPUs' graphics
capabilities.
"We will see a wholesale transformation of the PC-graphics market in the
coming year," said Dean McCarron, principal of market watcher Mercury
Research (Scottsdale, Ariz.). "Better pipelining and parallel processing and
other new features will boost rendering to a completely new level. We are
going from cartoon quality to the quality of a good painting."
On the processor front, Advanced Micro Devices will lobby for its newly
named 3DNow! floating-point instruction set extensions, supported in its
K6-2 processor. Centaur Technology's WinChip-2 processor, sampling
now, also supports the instructions.
G. Glenn Henry, president of Centaur (Austin, Texas), said AMD, Centaur
and National Semiconductor's Cyrix have struck a technology-sharing deal to
support the 3-D instruction-set extensions, though they have yet to announce
their plans. "Technically, it's a done deal, and we are moving ahead. It's up to
AMD to crank up the publicity engine," Henry said.
But the AMD techniques will soon see competition from Intel in the form of
the Katmai New Instructions, which provide similar floating-point instruction
extensions to enhance 3-D support on the Katmai version of the Pentium II.
Intel has indicated it will provide pre-release versions of Katmai systems to
software developers later this year; the chip is expected to hit the market
formally in 1999.
Key games developers say they will support both the Katmai New
Instructions and those of AMD. "Quake3 is being architected with small,
concentrated floating-point-intensive loops operating on batches that will get
large performance increases with either SIMD [single-instruction
multiple-data] instruction set," said John Carmack, lead designer at Id
Software (Mesquite, Texas), developer of popular games such as Doom.
"We are supporting K6 3-D instructions in Unreal, and that instruction set
looks quite well-designed, given the context-switching constraints," said Tim
Sweeney, founder of Epic Megagames Inc. "And for our next-generation
game engine, we'll definitely support KNI."
Sweeny added that "a lot of the next-generation rendering features that
require software assist-volumetric lighting, real-time radiant lighting and
curved surface tessellation-are ideal uses for KNI or K6-3D, since their
performance is limited by some tight inner loops that perform highly
parallelizable floating-point ops."
Features war
On the graphics-controller front, chip makers are fighting a features war in an
effort to gain the allegiance of key games developers. Nvidia, which has
enjoyed a burst of success with its Riva products over the past year, will find
more competition cropping up around it. S3, which was relegated to the
low-end last year after it encountered delays introducing new technology,
now claims it is back on track.
Then there is the coming of the Banshee 3-D accelerator from 3Dfx, which
has a solid reputation for high-performance 3-D chip sets and has garnered
something of a cult following among game enthusiasts. 3Dfx boasts 250 game
titles that are optimized to run on 3Dfx Voodoo, more than half of which use
the company's proprietary Glide API.
S3's Savage 3-D will bring the benefits of texture compression, a revamped
3-D pipeline and trilinear mip-mapping. Nvidia's Riva TNT, for its part,
boasts single-pass multitexturing capabilities and exceptionally high fill rates.
Game developers are divided on their enthusiasm for the new features.
"Trilinear is what you do when you don't have anything better to do with a
second texture unit. It is a relatively minor improvement," said Carmack of Id.
"Single-pass multitexturing helps Quake-style engines significantly, but there is
currently a lot of disagreement about exactly what feature sets are to be
supported in terms of iterators and color combining."
Sweeney of Epic was more upbeat. "Single-pass multitexturing is extremely
useful," he said. "On today's hardware, trilinear filtering isn't a very worthwhile
feature to use; however, as the rendering quality levels increase with future
generations, trilinear will soon be a mandatory feature."
S3 is betting its 0.25-micron Savage product will make up for time lost last
year when the company failed to introduce a follow-on product to its Virge
chip. While S3 still holds a lead in terms of number of graphics chips shipped,
it is losing design wins to competitors such as ATI Technologies, said
McCarron of Mercury Research. "This is a critical product for S3 to retain
their leadership position," he said.
Savage's attributes include the ability to perform, in one clock cycle, texture
compression as well as trilinear mip-mapping-a technique for smoothly
increasing or decreasing the level of detail in a texture-mapped surface as the
object moves toward or away from the viewer. The device also provides
high-quality 16-bit and 24-bit color rendering, hardware assist for DVD and
an integrated 60-MHz video port, according to the company.
S3 included trilinear mip-mapping filtering as a way to remove motion
artifacts and display smoother images. About 80 percent of the top games
being developed for the holiday buying season this year will use trilinear
mip-mapping, said Michelle Belusar, product-marketing manager for S3.
Indeed, Scott Sellers, co-founder and chief technology officer for 3Dfx, said
he expects most graphics controllers will soon support the technique. But he
said it's only one piece of the 3-D pipeline. "Trilinear is coming, but I have to
yawn because it's a very small step."
For its part, 3Dfx has begun sampling its long-anticipated Banshee, the
company's first single-chip OEM offering to integrate both 2- and 3-D
capabilities. It contain the same 3-D core as the current Voodoo 2 chip set
and adheres to the same software-legacy constraints as most other 3-D chip
companies.
Not everyone has jumped on trilinear mip-mapping bandwagon. Nvidia will
forgo the technique, aiming instead to improve visual quality by ensuring its
Riva TNT can do multiple textures and a related feature known as bilinear
bump-mapping in a single pass.
S3's Belusar said Savage will support bump-mapping and multiple-texturing a
"majority" of the time. 3Dfx's Sellers called single-pass multi-texturing the
"wave of the future."
Another feature that's emerging as texture data balloons in complexity and
size is texture compression. S3 has incorporated a 6:1 texture-compression
algorithm into Savage and has licensed the technology to Microsoft for
inclusion in the Direct3D 6.0 API, which is expected to arrive this summer.
Belusar said some games have textures that take up 40 Mbytes of data-a
level that calls for both compression and going out to the system memory via
the Accelerated Graphics Port (AGP) bus. Savage also has a FIFO buffer
memory that lets the graphics device constantly send out requests to the AGP
controller while simultaneously receiving texture data. That reduces latencies,
which can get as high as 200 clock cycles.
3Dfx will support S3's compression algorithm-but only because Microsoft
has opted to use it in Direct3D. "We'll support it as a subset of a newer
compression algorithm we're working on, but in terms of visual quality it
leaves a lot to be desired," Sellers said.
Each of the competitors plans to start shipping new 3-D devices in volume by
the third quarter, and each has its own set of challenges to overcome. For S3,
the fact that Savage has a 64-bit bus memory has drawn criticism.Nvidia says
moving to a 128-bit interface lets it achieve a maximum fill rate of 250 million
pixels/second. 3Dfx's Banshee will also support 128-bit as a way to feed
more data to the graphics controller and frame buffer memory, Sellers said.
Copyright (c) 1998 CMP Media Inc.
|
