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NVidia spins new twist for PC graphics

Posted: 14 Nov 2006 ?? ?Print Version ?Bookmark and Share

Keywords:NVidia? GeForce? GeForce 8800? DirectX 10? Windows Vista?

'Adrianne' is the world's first real-time, virtual celebrity based on model and actress Adrianne Curry, all rendered on the new NVidia GeForce 8800 GTX GPU.

PC graphics takes a new twist as NVidia Corp. rolls out its latest graphics processor. The GeForce 8800 uses a novel architecture based on pool of 128 simple processing units that can rip through graphics for Windows Vista as well as thorny tasks in technical computing.

NVidia's chip is the first to adopt the unified programming model for Microsoft's DirectX 10 software interface for graphics to ship with Windows Vista in January. Analysts give NVidia kudos on the design, but said they will wait to see competing parts expected in the next few months from archrivals ATI Technologies and Intel Corp. before they render a final judgment.

"This unified architecture will be a major shift in PC graphics," said Dean McCarron, principal of market watcher Mercury Research. "The NVidia part looks strong on paper, but we need to wait until all the products are out and running to determine who is ahead," he added.

Previously, graphics chips used separate arrays of custom hardware units optimized to handle tasks such as calculating vertex points or shading pixels. Sometimes chips bogged down when an application needed more resources for a particular process than a chip offered. Under the new architecture, data will stream across a generic pool of arithmetic logic units (ALUs) that can handle any graphics process needed.

Unified architectures
ATI and Intel parts are expected to have roughly similar unified hardware architectures for their DX10 devices. "Implementations will vary, but if you have a DX10 part it will likely have this basic capability," said McCarron.

NVidia is taking that model one step farther by creating a special mode where those ALUs can handle computing threads instead of graphics primitives. That opens the door to easier use of the chips in data-intensive technical applications such as medical imaging or oil and gas exploration. Those apps traditionally use banks of DSPs, FPGAs or custom vector processors, but are increasingly turning to highly parallel graphics processors.

"During the four-year process of designing this product, it became clear some people were increasingly using graphics to do non-graphics applications. But that's quite awkward because you have to pretend to write graphics code when you are not, so the thought was to do this more directly," said David Kirk, chief scientist of NVidia.

ATI has given signs it sees a similar opportunity. The company demonstrated use of its graphics chips for "streaming" applications such as grid computing recently, although it may not disclose its next-generation core until early next year.

Currently NVidia ships "a few thousand" graphics systems a year to users in a wide variety of technical computing markets. It hopes to expand that base when workstation and rack-mounted systems using the GeForce 8800 ship starting in January.

In its technical computing mode, the chip provides a thread scheduler in hardware and a facility for sharing cached data between ALUs. It lets programmers work in C rather than relatively arcane graphics languages currently used in scientific computing with existing graphics processors.

At 681 million transistors, the 90nm GeForce 8800 "is one of the largest semiconductors ever fabricated," said Kirk. "The biggest challenge was getting the performance increase we wanted without astronomical increases in power," he added.

Performance boost
The GTX8800 adapter card provides twice the performance of NVidia's current graphics adapter. It consumes 145W maximum and 116W on average. That compares to 116W max and 99W average on the last generation card.

The GeForce 8800 organizes its 128 ALUs into eight processing units with 16Kbytes cache per block. The 32bit, single-precision scalar processors have their own integer and floating point units and a full instruction set. Versions supporting double-precision math and additional ALUs are in the works.

"This is a very scalable design," said Andy Keane, general manager of NVidia's technical computing group.

The chip handles its own geometry and physics processing, offloading the tasks often run on a CPU or separate accelerator, respectively. The net result is in greater smoothness of lines due to better anti-aliasing and superior rendering of highly complex images, especially ones involving shadows, smoke, skin and hair.

The chip also supports new levels of high-definition video post processing, both for the H.261 and VC-1 codecs.

The GeForce 8800 comes in two flavors of 16x PCIe adapter cards. The 8800GTX sports a 575MHz core, 1350MHz shader block and up to 768Mbytes of GDDR3 running at 900MHz. It sells for $599.

The 8800GTS sells for $499. It includes 96 ALUs, a 500MHz core, a 1200MHz shader and up to 640Mbytes GDDR3 running at 800MHz.

- Rick Merritt
EE Times

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