Introduction

ATI has taken an indisputable technology lead with the release of the R300-based RADEON 9700 PRO. Not only has this product outperformed the best offerings of NVIDIA, Matrox and others, but it has provided a feature set that is considerably richer. For those who might think so, I want to reassure you that we have not turned into “fanboys”. A close examination of the performance and feature set of R300 establishes this technology lead we speak of, and it is a lead that simply cannot be argued with.



With that said, NVIDIA should be expected to answer back, and with the announcement of GeForce FX (NV30), they have responded. However, GeForce FX is still some time away from shipping and so for now ATI has the extreme high-end market as their own. We felt that it would be interesting to take a close look at R300, looking not only at the surface, but digging deep into the technology. In this two-part article we will first consider each of the 3D related technologies within the chip, from there examining the performance of not simply the whole chip, but each individual unit.

SmartShader 2.0 - Pixel Shader

The introduction of pixel shader standards brought about a change that went from wanting more pixels to wanting smarter, more advanced pixels. A variety of new operations were brought to the forefront with the use of pixel shader hardware, including division, subtraction, square roots and many others. These allowed game developers to produce dramatically more complex lighting, shadowing, and bump-mapping effects.

DirectX 9 has taken pixel shader functionality to a new level of complexity. There are several new operations available, in addition to greater overall flexibility. R300 follows the pixel shader 2.0 (PS2.0) spec almost perfectly, with the addition of greater instruction support. The following chart compares R300’s pixel shader to that of the pixel shader 2.0 specification. In certain cases R300 exceeds the PS2.0 specification, where in others it meets it exactly. In cases where R300 has greater support, it is likely the PS2.0 limitation exists due to another hardware vendor’s upcoming design finding such limitations.

PS 2.0 vs. R300
	Pixel Shader 2.0	R300
Max Textures	16	16
Instruction Slots	96	160
Color Ops	64	128
Address Ops	32	32