RADEON 8500 — Driven To New Heights — THG.RU

RADEON 8500 — Driven To New Heights

So far, the introduction of ATi’s Radeon 8500 has seemed more like a puzzle than a product launch. Consequently, it’s been hard to get a good general impression of this card and its potential. In early August, ATi distributed a small number of pre-production cards, but these samples were rather unconvincing and seemed far from finished. This pre-sampling phase was followed by a veritable shower of whitepapers in which ATi presented its new chip, bit by bit.

The real launch finally took place around the middle of October, with very positive results (for the most part). In some benchmarks, the card was able to beat Nvidia’s new flagship, the Ti500, by a comfortable margin. However, this victory was marred by incompatibility issues on Athlon systems, as well as by comparatively low Windows XP performance. The final blow came in the form of the discovery that ATi was cheating in certain benchmarks, skewing the results in their favor by unfair means. Apparently the OpenGL driver (v7191) uses a detection routine to identify the game Quake 3, triggering an undocumented manipulation of the MIP map handling. While this results in noticeably higher frame rates, the added speed comes at the cost of image quality, which suffers visibly. Lastly, the much-touted new SmoothVision FSAA method was not activated in this set of drivers, which only offer SuperSampling FSAA as it was implemented in the original Radeon.

This screenshot shows the degraded image quality of the «Q3 optimized» driver

The Second Attempt

ATi has now released a new driver (v7206). This new version addresses many of the problems from the first round of reviews: it resolves the Quake 3 «issue;» offers SmoothVision FSAA; and, enables 16tap anisotropic filtering. On top of that, it improves performance.

Smoothvision

Like Nvidia’s Quincunx, ATi’s «SmoothVision» FSAA technology is based on MultiSampling. This FSAA method allows for much higher frame rates than the SuperSampling method, which was used in the GeForce2 series and the older Radeon. For a more detailed explanation of these FSAA techniques, take a look at this article: High-Tech And Vertex Juggling — NVIDIA’s New GeForce3 GPU — Super-Sampling Anti-Aliasing.

ATi is taking anti-aliasing one step further, refining it a bit more. Since the MultiSampling FSAA technique always produces slightly blurred textures, it is inherently inferior to the SuperSampling method. ATi is attempting to tackle this problem by using SmoothVision, which lets the user choose between maximum quality or maximum performance. While the second option is obviously optimized for speed, the first uses larger textures and therefore requires more memory and more bandwidth. Additionally, the textures are filtered, producing a much crisper result.

Next to the usual 2x and 4x FSAA modes, the new drivers also offer settings for 3x and 6x. The «Quality» and «Performance» levels allow different maximum resolutions. Here’s a chart:

The following screenshots show the differences in detail:

A closer look at these images reveals the differences among the various FSAA implementations and settings. At 2x FSAA, the Ti500 does a better job of smoothing the jagged edges, but offers lower texture quality — even when compared to ATi’s performance setting. At the 4x setting, differences are very hard to make out — the results on both cards are nearly identical. Once again, the Ti500’s image is less crisp than the Radeon’s. This effect becomes even more pronounced when Nvidia’s Quincunx mode is used.

Smoothvision, Continued

ATi’s SmoothVision is aimed squarely at quality. Apparently (anisotropic) texture-filtering is enabled by default — unlike Nvidia’s solution. The ATi driver offers two settings for anisotropic filtering: ‘High,’ and ‘Highest.’ (More on that later.) The GeForce3 supports 16tap, 32tap, and even 64tap. Although these settings have theoretically been supported since the 12.xx Nvidia family of drivers, the drivers themselves lack a way to change them. The options can only be set by manually editing the registry, or with the help of freeware tools like NVMax.

Let me repeat: The «GeForce Ti500 — Xx FSAA — 64tap» mode is not available in the standard Nvidia drivers in this form. The reason behind this is unclear, as to why this level of quality is currently unavailable to the Radeon 8500.

Using the standard FSAA settings, the GeForce3 is roughly twice as fast as the Radeon 8500 — but with visibly lower image quality. Yet even with forced 64tap anisotropic filtering the Ti500 can maintain its lead over the R8500 — while offering outstanding image quality. In light of these results, it is unclear why Nvidia isn’t officially offering this setting.

At this point, we can conclude that ATi’s SmoothVision is slower than Nvidia’s FSAA method. The following benchmarks prove that this has nothing to do with filtering.

Anisotropic Filtering

Anisotropic filtering offers much crisper textures than other methods. Even when using trilinear filtering, the floor textures in Quake 3 appear to be very smudged at a certain range. The much more extravagant anisotropic filtering lessens this effect, though at the cost of speed.

Nvidia and ATi use different philosophies in defining their anisotropic filtering. ATi claims that the Radeon 8500 can do 16tap anisotropic filtering while Nvidia speaks of 64tab of GeForce3. But they mean the same thing — in the end.

ATi’s 16 stands for the ratio, or level of filtering employed. Some background information: bilinear filtering requires 4 texels (displayed pixels of a texture, which additionally may already have been manipulated by a light/ pixel shader). Trilinear uses 8 texels, while anisotropic uses 16, 32, 64,128, or more texels. The number in Nvidia’s documentation for the Ti500 refers to the number of texels used, e.g. 64tap for 64 texels. On the Radeon, anisotropic filtering uses blocks of already-blended samples [bilinear (4) or trilinear (8)]. Therefore, the highest quality setting on the Radeon 8500 is 16:1 bilinear (64tap). This means that the filter uses 16 blocks of bilinear-filtered texels (16 blocks x 4 texels = 64). Until recently, the ATi drivers had the settings ‘High’ (4:1 / 16tap), and ‘Highest’ (16:1 / 64tap).

The quality comparison yields an interesting result: ATi’s 16tap is nearly identical to Nvidia’s 64tap setting! And thatґs no Surprise (see text above).

A surprising result! Enabling anisotropic filtering only slows the Radeon down by 7fps. At comparable quality (64tap), the Ti500 loses almost 80fps! Even the relatively moderate 16tap setting costs the Ti500 a full 30fps.

According to ATi, R8500’s impressive performance when using anisotropic filtering is the result of a dynamic filter implemented in the driver. This means that the card doesn’t necessarily use the highest possible quality filter for a given texture. For example, if you are standing right in front of a wall in a first-person shooter, the driver will only use bilinear filtering (4 texels), since the difference in quality when using anisotropic filtering (64 texels) would be all but unnoticeable (a claim which remains to be proven). In other situations, when looking down a long corridor, for example, the high quality-filter is activated. Since no additional information is available at the moment, here’s a quote from ATi’s David Nalasco:

«The Radeon 8500 only uses the full number of samples in parts of the image where they are really needed, which saves bandwidth while still delivering full anisotropic image quality — just another example of the ‘intelligent architecture’ that saves bandwidth whenever possible.»

We’re still awaiting a reaction from Nvidia. There is some information that Nvidia is using trilinear anisotropic filtering in GeForce3 compared to bilinear anisotropic filtering in ATIґs R8500. Nvidia says that they are using 16 texel samples for triliniar anisotropic filtering, and 8 for bilinear. However, this is hard to estimate because there are no official driver settings yet.

Test Setup

Benchmarks

Giants

The Radeon’s new driver gives it a tangible performance boost in ‘Giants.’ Nonetheless, the GeForce3 cards continue to dominate this benchmark.

Max Payne

Here again, the new drivers improve performance. In the higher resolutions, it is almost able to catch up to the Ti500.

Quake 3

The grayed results of the v7191 drivers indicate that these scores aren’t directly comparable to the newer version, since the older driver automatically reduces texture quality in this game. ATi faced harsh criticism for this hidden «optimization,» and has subsequently removed it from the current revision. Ti500 and R8500 are now practically on the same level.

3DMark2000

In ‘3DMark2001,’ the new drivers can once again raise the performance bar a notch. The Radeon 8500 now has a firm lead over the Ti500 in this important benchmark.

Conclusion

The Radeon’s new drivers are a step forward in every respect. The performance has improved, and the very controversial ‘Quake3 optimization’ has been removed from the driver. A very impressive aspect is the Radeon’s performance when using anisotropic filtering. The R8500 simply leaves the competition by Nvidia in the dust.

SmoothVision, on the other hand, still doesn’t seem completely convincing. Although the quality is spot-on, the performance is too low. Nvidia also has some work to do in regard to FSAA, since the highest attainable quality is only available after a registry hack. Judging from the latest Nvidia leaks, it looks as though settings for anisotropic filtering will make their way into one of the upcoming driver releases.

So, as before, the race remains exciting, and is still too close to call. The Radeon 8500 is definitely serious competition for Nvidia!