ATI Technologies Inc.
on Wednesday introduced its Radeon X800 XT Mac Edition, a new US$499 graphics card specifically for Power Mac G5 systems. The new card occupies a single expansion slot and can provide double the performance of a Radeon 9800 card, according to ATI. Outfitted with an dual-link DVI port and an Apple Display Connector (ADC) port, the Radeon X800 XT Mac Edition can drive a 30-inch Apple Cinema HD Display and an older 23-inch Apple Cinema HD Display side by side.
The Radeon X800 card is built around ATI’s R420 graphics chip architecture. Manufactured using a 0.13 micron copper low-k process, the chip supports GDDR3 memory and talks to the Mac through an 8x AGP Pro interface. Using a built-in fan to cool the circuitry down, the X800 has a lower profile and a considerably smaller board design than the Nvidia 6800 cards Apple currently offers Power Mac G5, which is why it only occupies one card slot, instead of the two the Nvidia alternatives occupy.
Under the hood
ATI bills the X800 as the world’s fastest AGP-based Visual Processing Unit (VPU). It features 16 pixel pipelines, compared to 8 in the 9800 Pro; a 475MHz core speed, compared to 375MHz for the 9800; 1GHz memory data rate, compared to 675 for the 9800; six vertex engines, compared to the 9800’s four; a 7.6 gigapixel per second pixel fill rate, compared to 3.0 for the 9800; 32GB per second memory bandwidth, compared to 22 GB per second for the 9800, and the ability to transform 712 vertices per second, compared to 340 for the 9800. All this equals about twice the overall performance of the 9800, according to ATI.
“We have this parallel-processing machine — we can send a whole bunch of instructions simultaneously,” explained Stan Ossias, senior product manager at ATI. “The more pixel pipelines you have, the faster you’re able to execute.”
The X800 also yields support for the latest generation of pixel and vertex shading capabilities and other visual tricks supported by ATI. 3Dc, for example, is a “normal map” compression technology that yields dramatically more realistic details and textures in games. It’s not yet supported by any Mac games, but ATI figures it’s just a matter of time before some of them are ported.
Smartshader HD is ATI’s terminology for its pixel shading technology, which gains some improvements in this release. Pixel shading is a complex technique used to render realistic lighting effects, but its dependence on low-level assembly code has stymied some developers in the past. ATI’s Chris Bentley, who heads up the company’s 3D Mac driver development, told MacCentral that ATI’s making it easier to expose this important feature.
“It doesn’t take a lot of handholding to get the shading technology. Part of that is thanks to the good engineering that went into the design languages,” he said. ATI’s X800 architecture supports OpenGL — the 3D rendering technology used on the Mac — and DirectX, which is used in Windows.
What’s more, the X800’s ability to execute shading-related instructions is much more advanced than the 9800’s, said Ossias. The X800 can execute 1,536 shading instructions per pass, ten times the amount of the 9800.
Smoothvision HD is ATI’s catchphrase for its graphics hardware’s ability to to perform full-scene anti aliasing (FSAA), a technique used to smooth the jagged edges of geometric 3D objects. The X800 gets a boost here with support for new anti-aliasing techniques like sparse sample pattern with gamma correction and centroid anti-aliasing. Anisotropic filtering — which yields more realistic textures displayed in perspective — also gets improvements, with 16x support using adaptive heuristics.
ATI also vaunts the X800’s support of HyperZ HD, a technology that predicts what’s shown on screen and hides what isn’t. The chip can figure out when 3D objects aren’t actually able to be seen by the viewer, and stops rendering them. HyperZ HD has been optimized for performance at higher resolutions and rejects more occluded pixels than before, rendering better speeds. It’s also completely transparent for software developers, happening without needing any additional application code.
Not just for gaming
While Macintosh gaming enthusiasts will enjoy the X800’s high-speed performance and new capabilities, gamers aren’t the only ones who stand to benefit from the card. As more and more Macintosh creative applications leverage OpenGL — especially with Mac OS X v10.4 “Tiger’s” forthcoming release — creative professionals will also see marked improvements in performance by switching to a faster card, according to Ossias.
Apple’s own Motion software, Luxology’s Modo, Maya, Cinema 4D and Hash Animator are just a few examples of the content creation software that will yield improved performance with a faster 3D graphics card; as will any applications that support Tiger’s forthcoming “Core Image” graphics architecture.
“Software written with instructions to take advantage of the graphics engine are taking prominence in the Mac space,” Ossias told MacCentral. “Apple is way ahead of the game here by having a graphics architecture like it does in Tiger. Lots of applications will take advantage of that.”
“On the Windows side, the operating system hasn’t yet begun to care about this stuff,” added Bentley.
The right card for now
With ATI already emphasizing the Radeon X850 to its PC users, isn’t the X800 a bit late to the game? Ossias says no.
“We have a very user-centric design philosophy,” said Ossias. “Our design goal with the Radeon X800 XT Mac Edition was to develop a quiet, cool single-slot board that fits inside a Power Mac G5. If there was a huge upside or extra performance by using the 850 instead, we would.”
Ossias says the X800 card — despite its huge performance increase — actually runs quieter than the Radeon 9800 Pro Mac Special Edition card. Users who are considering replacing the stock Radeon 9600 card included with some Power Mac G5 configurations will likely notice a modest increase in noise, since their cards use a silent heat sink to cool instead of a fan.
A lot has been made of PCI Express, a new parallel-based expansion port standard that offers greater performance than the AGP or PCI-X architecture found in current Power Macs. Some see the absence of PCI Express as a shortcoming in Apple’s pro desktop system design, especially as PC motherboard manufacturers increasingly support the new standard. Ossias admits that PCI Express has some benefits, but downplays its real-world usefulness, for now.
“We haven’t been topping out the capabilities of AGP,” he said. “In theory, bidirectional PCI-X would work faster, but it’s a different story for application software.”
Ossias told MacCentral that ATI will continue to sell its Radeon 9800 Pro Mac Special Edition — a version of the previous generation high-end card specifically for Power Mac G5 users.
ATI said the Radeon X800 XT Mac Edition would be available for purchase through its Web site and through Apple retailers. The card will also be showcased at ATI’s booth at next week’s
Macworld Conference & Expo
in San Francisco, Calif.