Deeper with the Radeon X1900 Series
PCI Express x16 graphics cardsChipset X1900 512 MB, 256 bit
It's only been three months into the year 2006, but the next generation of graphics chipsets are already here. This time around, the first salvo is from ATI, in the form of the Radeon X1900 series formerly known as R580. When the very late Radeon X1800 came out several months ago, most people agree that the chip to watch out for is not the Radeon X1800 (or R520) but the R580. Architecturally, the two are very similar, but the R580 is equipped with more shader units per pixel pipeline than the R520 - 48 shader units in all.
Both the Radeon X1800 and X1900 signify a new move in realtime consumer 3D graphics - a more shader oriented approach. Granted, shaders is not a new thing, it's been present ever since DirectX 8 made its debut in realtime consumer 3D graphics. However, due to limitations of graphics hardware and API, these shaders are very simple in nature and not used very extensively. With the move to DirectX 9 and SM 2.0 / 3.0 and the rise of shader processing power, shaders are now used more extensively than ever before. In fact, some of the newest 'eye candy' effects present today like motion blur, depth of field and high dynamic range rendering which until now remains in the realm of offline rendering is now possible with shader capable graphics hardware.
If shader capable graphics hardware is so abundant this days, what makes the Radeon X1800 and X1900 unique? It's their design, the Radeon X1900 with its 48 shader units in particular. Unlike the GeForce 7 series from NVIDIA, ATI decided to keep the number of pixel pipelines at 16 for both the Radeon X1800 and X1900. Both cards rely on a higher operating speed (MHz) to maintain fillrate parity with NVIDIA's GeForce 7. On the other hand, NVIDIA chose to equip the GeForce 7 series with 20 pixel pipelines for GeForce 7800GT and 24 pixel pipelines for the 7800GTX, respectively. With more pixel pipelines, NVIDIA GeForce 7 can offer higher frame rates than the Radeon X1800 or X1900 on texture dependent games. However, on shader heavy games, the Radeon X1800 and X1900 should provide the same level of performance to the GeForce 7800GTX. Most likely even higher in the case of X1900. ATI is 'betting' that the clock speed difference is sufficient enough for their cards to have the same level of performance compared to the GeForce 7. But when it came to shaders, the Radeon X1900 should be significantly faster than the GeForce 7800GTX. This makes both the Radeon X1800 and X1900 unique, in a manner marking the transition to even more complex and comprehensive use of shaders in realtime 3D graphics.
There's a reason why ATI chose to push shaders. Textures take up space, but more importantly, they take up bandwidth. We're already seeing 512 MB graphics cards today, which should be the norm this year with the coming of new games and Windows Vista. However, unlike capacity that's ever growing, memory bandwidth is relatively 'stuck' and have virtually hit a brick wall - even the fastest GDDR4 available can only offer 10 - 11 GBs of bandwidth. With a 256 memory controller, that's about 40 - 44 GBs of bandwidth total. Now look at the GeForce 7800GTX 512, a card that has about 50 GBs (or so) of bandwidth. This is the upper limits of current memory technology. Our article last month (which you can read here) shows that to get a significant increase in performance, either from a higher clocked core and / or more pixel pipelines out of the current architecture, we need to have more than that. There's no point of putting more pixel pipelines with the bandwidth available today.
Furthermore, games today are focusing on shaders more and more. ATI feels that this is the area next generation of graphics cards should focus on. Not just pixel or texel fillrate. The Radeon X1K series are actually the first SM 3.0 capable parts from the Canadian based manufacturer. The series span across different levels, from the entry level X1300, the mainstream X1600, and the high end X1800 and X1900. It's about time too, since rival NVIDIA have had SM 3.0 parts for more than one year now with the GeForce 6 and 7 series. ATI felt SM 3.0 was not needed a year ago, and they are right with so many games and developers still targeting SM 2.0 hardware or still in the process of transitioning from DirectX 8 to DirectX 9. Games are just beginning to utilize SM 3.0, despite the already widespread use of SM 3.0 capable GeForce 6 and 7 series. Even now, there are only a number of titles available today that utilize SM 3.0. ATI feels the time has come for SM 3.0 to take center stage, that's why they're introducing the X1K series. This move in the desktop arena is in sync with their overall strategy, including developments on the console market. The Xenos chip in the Xbox 360 shares many similarities with the X1K series. The similarities between the two products should ease development on two platforms for game developers, at the very least make porting code between platforms easier and take less time.
Of course, while having more shader power is nice, that power can only be unleashed with the right software. Since games fully utilizing SM 3.0 potential are yet to appear, we really don't know just how good (or bad) ATI's design decision for the X1800 and X1900 is until those games appear on the market. So, the X1800 and X1900 come with more than just raw shader power. It offers higher quality filtering with less optimization, adaptive antialiasing for transparent textures, high dynamic range rendering with anti aliasing and overall faster antialiasing performance. We'll be looking into several of those claims in this article.
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