Essentially, to provide really complex shader effects in real time, you want to avoid making multiple rendering passes, at least in the traditional sense of full passes through the GPU pipeline. Multi-pass rendering is nifty because it overcomes a lot of technical limitations, but it’s a performance killer because it duplicates lots of work unnecessarily. In order to produce more complex effects, the R300 would have to resort to multi-pass rendering. The pixel shaders on the R300 chip are limited to program lengths of 64 instructions, which simply isn’t enough to create some of the more compelling shader effects developers might want to use. One of the NVIDIA GeForce FX’s key advantages over the Radeon 9700 is its ability to execute pixel shader programs as long as 1024 instructions. The most significant piece of new technology in the R350, however, is more than a simple performance tweak. (That is, info about a pixel’s position on the Z axis.) ATI says this cache has been optimized to work better with stencil buffer data, which should help when developers use stencil shadow volumes to create shadowing effects in future games like Doom III. Finally, the R350’s has an improved cache for Z-buffer reads and writes, to aid in the bandwidth-intensive task of handling pixel depth information. Also, the company has tuned the chip’s memory controller to better arbitrate reads and writes during heavy use, which should especially help performance when rendering antialiased pixels. The clock speed of the R350 chip is 380MHz, while the R300 peaked at 325MHz in the Radeon 9700 Pro. Hard to argue with that.ĪTI has taken several measures to allow the R350 to put its memory bandwidth to good use. ATI has achieved more throughput than any other consumer graphics chip, and they’ve done so without resorting to a Dustbuster appendage. No, that’s not a huge gain in terms of bandwidth overall, but it’s not bad. The Radeon 9700 Pro, by contrast, topped out at 19.8GB/s. The Radeon 9800 Pro will debut with an effective 680MHz memory clock speed, which gives it a very healthy 21.8GB/s of memory bandwidth.
The R350’s 256-bit DDR memory interface runs at a higher clock speed, which allows the chip to have even more memory bandwidth than the Radeon 9700 Pro. Like the R300, the R350 is manufactured using 0.15-micron process tech, and like the R300, it has 8 pipelines with one texture unit per pipe. The key things you need to know about the R350 chip are fairly basic. If you want to understand the technology from which the R350 is derived, please read our 9700 review.
We’ve already reviewed the Radeon 9700 Pro in some depth, and I will try to avoid repeating myself here. R350 is, as you might expect, derived from ATI’s R300 chip, which powers ATI’s Radeon 95 lineups. The Radeon 9800 Pro is based on the chip code-named R350. Read on as we examine the 9800 Pro in detail, exploring the performance and technology behind ATI’s latest and greatest. With fast 256-bit DDR memory, improved pixel shaders, and more efficient use of memory bandwidth, the Radeon 9800 Pro looks to be the new king of the hill. The new Radeon 9800 Pro is all about solidly winning the graphics lead for ATI, and these cards are set to hit store shelves this month-quite possibly before any of the high-end GeForce FX cards arrive. NVIDIA’s GeForce FX 5800 Ultra may have captured at least part of the technology and performance titles for itself, but the cards are so rare, we haven’t even been able to secure one for review. A TI’S RADEON 9700 PRO HAS been a resounding success, capturing the leads in both graphics technology and performance for ATI upon its introduction last fall, and holding the crown to today-at least in terms of products shipping in volume.