Graphics chips add up to a good looking future

Graphics chips add up to a good looking futureThe PC graphics market is one of the most challenging for silicon designers. The market is overcrowded, competition fierce and technological changes blistering. All to keep the gamers happy, says Roy Rubenstein presses the ‘game on’ button
It’s a whapping ass math engine.” That’s how Jon Peddie describes the chip at the heart of the next generation Sony Playstation
And he should know, Peddie heads Jon Peddie Associates, the US graphics market research firm and he has seen the new machine in action.
For all the complexity characterising the 3D graphics market, Peddie believes it all boils down to one thing: maths. “It requires lots and lots of divides in full floating point and lots of multiply/accumulates.”
The Sony-Toshiba Playstation chip, with its 128-bit Risc CPU and ten floating point engines, has achieved just that. “They’ve got it, they’ve understood,” says Peddie.
The chip is also an example of the increasing diversification in the 3D graphics market, says Peddie. The other, somewhat contradictory trend taking place is market consolidation, the result of fierce competition among the 50 or so 3D-chip companies. “Companies are being acquired, going out of business or just changing their model.”
That so many 3D graphics companies continue to pursue the PC market is due to the potential prize on offer. Even a small slice is worth having of the 90 million PCs with 3D graphics to be sold this year.
“There is nothing as important. It is where the volumes are,” says Peddie. John Metcalfe, programme manager for PC chip products for UK graphics firm VideoLogic, agrees: “It [the PC market] is the most dynamic market that graphics works in.”
The key driver for PC graphics is games. The number of gamers that insist on having 3D graphics is relatively small but these early adopters are tremendously influential. “They may buy one graphics board but they influence the sale activities of their peer group,” says Peddie. It is these “sniffly brats” with their challenging demands that drive 3D-chip companies like VideoLogic and US firm 3Dfx.
Yet, however important the gaming market, the influence of 3D graphics does not stop there. The PC desktop graphical user interface planned for Windows 2000 means that 3D graphics will enter mainstream use. “The line between the user interface, the Web and 3D graphics will disappear,” says Tony Tamasi, 3Dfx’s director of product marketing.
The result is graphics performance advancing at an astonishing pace. “We are beating Moore’s Law,” says Metcalfe, with performance doubling every year rather than 18 months.
“The latest Voodoo 3 can draw 8 million triangles/s and has a fill rate of 366 million textured pixel/s,” says Tamasi. He expects 700 million textured pixels a second by next year and 1.5 billion a second in 2001. Toy Story, the animated film, involved rendering 48 million polygons a frame, all done off-line.
Meeting such a real-time performance target requires advancements at the PC system level. From this perspective, the host processor, or CPU, is the most important component, letting you do more with the graphics, says Tamasi. “It calculates the artificial intelligence of games, the physics such as collision detection, and the lighting.” 3Dlabs hits the Jetstream
UK graphics chip developer 3Dlabs targets high-end workstations and the PC.
It’s latest workstation architecture, Jetstream, comprises two devices: Gamma and Glint. The Gamma G3 chips perform the graphics tasks normally carried out by the host CPU. “In games there is not much geometry to calculate,” said Tim Lewis, 3Dlabs’ director of business, Europe. For CAD applications, requiring greater accuracy, the number of polygons making up the image is much greater.
The output of the Gamma chip is passed to the Glint which turns triangles into pixel data. The latest Glint R4 chip is an enhanced version of Permedia 3, 3Dlabs’ high-end PC graphics chip. It is capable of handling 250 million textured pixel/s.
For demanding CAD applications these two devices can be scaled to increase performance. The largest set-up is seven G3s and eight R4s.
The recent instructions added to the Pentium III and the K6 microprocessors have boosted performance between a factor of two and four. A Pentium II resulted in 4 million triangles/s while a 500MHz Pentium III boosts it to 10 million, says Tamasi. “To hit 50 million triangles/s the CPUhas to continue to get faster.”
Faster CPUs increase the competition for access to the main memory. “At the end of the day, it is all about the speed of the main memory,” says Peddie.
For graphics the main memory holds such items as command, geometric and lighting data. Having faster CPUs has resulted in today’s typical 100MHz 64-bit-wide main memory becoming saturated.
The move to memories like PC-133 and Direct Rambus, with its 1.6Gbyte/s bandwidth, promises some respite but 3D-chip developers expect this to be temporary.
To aid the memory accesses, the Intel-inspired AGP bus performance is set to double this autumn. The AGP 4x, to work alongside Direct Rambus memory, will offer a bus bandwidth of 1Gbyte/s.
Exploiting the AGP bus, texture data can be placed in the host memory instead of the graphics IC’s local memory. This not only reduces system cost, it allows special effects to be introduced using the main CPU. However, this further loads main memory.
The writing is on the wall, claims Tamasi. Graphics vendors are slowly being forced to be increasingly clever since “at some point we are going to run out [of memory bandwidth]”.
One company that has already taken the plunge is VideoLogic in its PowerVR architecture. It uses more complex graphics processing to limit main memory accesses. Here, according to Metcalfe, all the triangles that make up a small block of an image are processed on chip and only the front-most textures, those known to be visible on-screen, are drawn, saving on memory access es. “It offers the best use of a scarce resource,” claims Metcalfe.
The stage is set for some radical architectural changes in the coming years. If 3D is maths, says Peddie, the logical extension is what companies like PixelFusion is doing.
What PixelFusion is developing is a sliver of silicon with thousands of arithmetic logic units on-chip “Then the concept of a graphics engine will be lost in a sea of processors,” says Peddie.

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