As we mentioned earlier, ATI has already implemented a solution to aid the processor in determining which polygons will be visible in a rendered scene. Similarly, NVIDIA has also implemented a form of Hidden Surface Removal with their GeForce3 product (Lightspeed Memory Architecture). Before 3dfx keeled, they were also working on an HSR implementation for their drivers. There is no question about it - hidden surface removal is part of the key to maximizing the limited capacity for memory bandwidth on today's powerful graphics processors. The benefits to the tile-based rendering scheme do not stop there, though.

Because the PowerVR architecture runs all texturing and shading operations internally at 32-bit precision, the quality of 16-bit output is actually enhanced. In immediate-mode rendering solutions such as the GeForce or RADEON architectures, multi-pass rendering results in textures being dithered to 16-bit. As increasing numbers of dithered layers are applied, the image quality worsens. KYRO II, on the other hand, benefits from its on-chip 32-bit mini-frame buffer that allows multi-pass rendering at full 32-bit precision without the performance penalty suffered by immediate-mode solutions - remember, 32-bit precision consumes twice the bandwidth of 16-bit on these architectures. Considering the lack of spare throughput, this benefit is very valuable.

The same on-chip tile buffer that keeps the 16-bit quality so clear also makes anti-aliasing much more efficient than competing solutions. Rather than rendering a super-sampled, high-resolution scene into the external frame buffer, the KYRO II simply renders the super-sampled image at 2x or 4x the target resolution. The final down sampling does not impact performance, since this extra step is already part of the pipeline. For 2x anti-aliasing, the image is filtered on either the X or Y-axis, while both X and Y are filtered for 4x mode.

FSAA fans should be happy to see that even under the very taxing MAX quality Quake III benchmark, the KYRO II is able to deliver playable frame rates in both 2x and 4x modes. Wisely, Hercules has limited 2x mode to 1280x1024 and 4x to 1024x768, since any resolution above these would be decidedly unplayable.