Imagination Technologies / STMicro PowerVR Series 3: KYRO

KYRO Specifications

• 12 million transistors
• 0.25 micron process
• 125 MHz core / memory clock
• 2 Pixel Pipelines
• 250 megapixel/s fillrate (750 megapixel/s effective fillrate)
• Support for 16-64 MB of SDRAM or SGRAM
• 128-bit data path to memory (2GB/s bandwidth)
• 32-bit z-buffer
• Tile rendering architecture
• Full Scene Anti-Aliasing (2x and 4x)
• Environment Mapped Bump Mapping (EMBM)
• 8-Layer Multitexturing
• Motion compensation support
• Support for AGP 4X, SBA, DiME
• DXTC Texture Compression
• Full OpenGL ICD

A quick glance at those specs may ellicit a "Are you kidding me?" initial response from many of you. Afterall, 125 MHz, 2 pixel pipelines, 250 megapixel/second fillrate, and a 0.25 micron manufacturing process sounds a lot like an NVIDIA RIVA TNT2 (not ultra) which has been out for over a year. But look closer and things quickly become interesting - the key is the tile rendering architecture, which we'll discuss in depth a bit later.

For now, note the 750 megapixel/s "effective" fillrate. Never before have we seen manufacturers quote an "effective fillrate" number as part of their specs. The simple reason is that for traditional 3D accelerators, the actual or effective fillrate never exceeds the theoretical fillrate. Of course, the KYRO can't run faster than its theoretical limitations. Rather, the PowerVR tile rendering architecture operates more efficiently than a traditional accelerator, allowing the KYRO, with its "lowly" 250 megapixel/s fillrate, to perform like a traditional accelerator with a fillrate of 750 megapixel/s. At least, that's what Imagination Technologies and STMicro claim, but we'll have to test that claim with real games first. Once again, the key is the tile rendering architecture that allows the KYRO to acheive this seemingly impossible feat.

Now let's take a look at that 125 MHz memory clock, which results in a memory bandwidth of 2GB/s, a far cry from the 5.3GB/s of the GeForce 2 GTS and Voodoo5 5500 or even the 2.7GB/s of the GeForce SDR. Much has been made of the GeForce 2 GTS and GeForce SDR having their fillrate limited by memory bandwidth at higher resolutions - our Overclocking the GeForce 2 GTS Guide illustrates this fact quite clearly. Yet the KYRO scoffs at NVIDIA and 3dfx and then gets away with it by using a more efficient architecture. Yet again, the key is the tile rendering architecture and its ability to use memory bandwidth much more efficiently than traditional 3D accelerators.

The rest of the specs are pretty typical, but we can see that Imagination Technologies threw in just about every feature that other 3D accelerators use, including Environment Mapped Bump Mapping (EMBM) that Matrox popularized with their G400, Full Scene Anti-Aliasing that 3dfx has been hyping for over a year and provided in the case of the Voodoo5 5500 by their proprietary T-Buffer, and DXTC Texture Compression that S3 started with S3TC on the Savage 4 that is just now showing its benefits to gamers. AGP 4X/2X/1X are all supported, as is side band addressing and texturing straight from system memory.

The full OpenGL ICD mentioned above is notable, not because it is something special in the industry today, but rather because Neon250 (PowerVR Series 2) users had to deal with OpenGL miniports - KYRO brings the PowerVR series back in line with the rest of the industry.