It’s got the Microsoft name, but the real star of the Xbox game console is nVidia and its pair of audio and video chips, which will top anything seen on a PC before.
The Xbox is largely built from existing parts used in personal computers, but Microsoft hired nVidia (NVDA) to produce not only a special 3-D graphics chip for the Xbox, but an audio and I/O controller as well. The chips, now complete, will offer performance the PC can’t approach.
So even though the XGPU is based on nVidia’s forthcoming NV20 chip that will be used in PCs, its performance is considerably faster than its PC brethren because there are no AGP video bus and north bridge in the way. The XGPU and CPU will both be directly accessing each other via the same high-speed memory with no buses in the middle.
The CPU and Xbox Graphics Processor Unit (XGPU), nVidia’s name for the graphics chip, share the same chunk of 64MB of 200MHz double-data rate (DDR) memory. That memory is twice as fast as memory normally used in PCs and there’s no bus between the graphics chip and CPU, which will yield performance well beyond the capabilities of the PC, nVidia and Microsoft claim.
The XGPU will be able to animate 125 million polygons per second. NVidia’s current top chip, the GeForce 2 Ultra, maxes out at 31 million polygons per second, and Xbox-like performance isn’t likely to happen on a PC any time soon.
“There’s absolutely no way you could render 125 million polygons a second across an AGP bus,” said Tony Tomasi, director of product marketing at nVidia. “The entire architecture of the XGPU is built around unified architecture where it shares memory with the processor, as opposed to shuttling it across a bus. So that changes the way the whole thing works.”
But Jon Peddie, president of Jon Peddie Associates, an analyst who specializes in the graphics market, said the XGPU may be faster than the rest of the system.
Peddie said Microsoft is making a mistake in raising expectations of quantum leaps in gaming, which Sony did with the PlayStation 2 and then didn’t exactly deliver.
“The risk for Microsoft is that they run the risk of raising expectations to a point that users are going to say ‘that’s it?'” he said. “That’s what’s happening to the PlayStation 2 now. Sony ran a bunch of experiments and made a lot of statements about performance, but in the delivery of actual product and actual games, it didn’t live up to expectations.”
NVidia’s second chip is the Media Communications Processor (MCPX), which handles audio, input/output and the broadband connection. Although known for its graphics chips, nVidia’s first processor, the NV1, was an integrated processor that handled sound, video and I/O.
The company says its graphics experience translates to sound and I/O nicely.
“As it turns out, networking and sound are similar to graphics,” Tomasi said. “Both tend to be problems about moving a large amount of data around quickly and doing some computation to that data.”
Tomasi claims the MCPX is far more advanced than any sound chips on the market by supporting 64-channel positional audio and real-time Dolby Digital encoding. By being able to encode game audio in Dolby Digital, game sound can be output to a home stereo amplifier that supports Dolby Digital, the same surround sound used by DVD, and games can have true surround sound.
The MCPX is the true breakout technology and may be a sleeper hit for nVidia, according to Peddie.
“It is an amazingly powerful part,” Peddie said. “The sound is just gonna knock your socks off. If the game developers put the sound in their games, which they will want to do, it will play games with extraordinary 3D sound. The Xbox has the potential of being the ultimate home entertainment system.”
The chips were released to manufacturing earlier this week and will be back to nVidia by the end of the month for testing. If there are any final bugs, they’ll be fixed, and then test systems will go out to developers by spring. Xbox is expected to ship this fall in the United States and Japan.
