ATI Radeon X1800 XT CrossFire Evaluation

Intro, Specifications & Related Info

The onslaught of ATI announcements this quarter continues today, with the official unveiling of the Radeon X1800 XT Master Edition graphics card -- the "missing link" necessary to run a pair of X1800 cards in a dual-GPU CrossFire configuration. From the end of September '05 through to today, ATI has announced and released a top-to-bottom line-up of graphics products in rapid succession, in an effort to bolster their product lines in time for the peak holiday buying season.

But ATI's intentions aren't just about getting products on store shelves in time for Santa to place them under the tree. In frank conversations with representatives from ATI, we were also told that the company's recent sequence of releases is about delivering on its promises. It's no secret that ATI has had a rough time bringing the CrossFire and the X1K family of products to market, and they've suffered because of it.  But the company seems committed to resolving their past problems, and re-ascending to the top of the 3D food-chain; the position aggresively wrestled from their grasp by NVIDIA's GeForce 7 series and SLI technology.  The next step to achieving their goal, is delivering Radeon X1800 CrossFire, and the company is poised to do just that.  Read on and feast your eyes on the best ATI has to offer...for now.

ATI Radeon X1800 & CrossFire
Features & Specifications
Features - ATI Radeon X1800
• 321 million transistors on a 90nm fabrication process
• Ultra-threaded architecture with fast dynamic branching
• Sixteen pixel shader processors
• Eight vertex shader processors
• 256-bit 8-channel GDDR3/GDDR4 memory interface
• Native PCI Express x16 bus interface
• Dynamic Voltage Control

Ring Bus Memory Controller
• 512-bit internal ring bus for memory reads
• Programmable intelligent arbitration logic
• Fully associative texture, color, and Z/stencil cache designs
• Hierarchical Z-buffer with Early Z test
• Lossless Z Compression (up to 48:1)
• Fast Z-Buffer Clear
• Z/stencil cache optimized for real-time shadow rendering
• Optimized for performance at high display resolutions, including widescreen HDTV resolutions

Ultra-Threaded Shader Engine
• Support for Microsoft DirectX 9.0 Shader Model 3.0 programmable vertex and pixel shaders in hardware
• Full speed 128-bit floating point processing for all shader operations
• Up to 512 simultaneous pixel threads
• Dedicated branch execution units for high performance dynamic branching and flow control
• Dedicated texture address units for improved efficiency
• 3Dc+ texture compression
_o High quality 4:1 compression for normal maps and two-channel data formats
_o High quality 2:1 compression for luminance maps and single-channel data formats
• Multiple Render Target (MRT) support
• Render to vertex buffer support
• Complete feature set also supported in OpenGL 2.0

Advanced Image Quality Features
• 64-bit floating point HDR rendering supported throughout the pipeline
_o Includes support for blending and multi-sample anti-aliasing
• 32-bit integer HDR (10:10:10:2) format supported throughout the pipeline
_o Includes support for blending and multi-sample anti-aliasing
• 2x/4x/6x Anti-Aliasing modes
_o Multi-sample algorithm with gamma correction, programmable sparse sample patterns, and centroid sampling
_o New Adaptive Anti-Aliasing feature with Performance and Quality modes
_o Temporal Anti-Aliasing mode
_o Lossless Color Compression (up to 6:1) at all resolutions, including widescreen HDTV resolutions
• 2x/4x/8x/16x Anisotropic Filtering modes
_o Up to 128-tap texture filtering
_o Adaptive algorithm with Performance and Quality options
• High resolution texture support (up to 4k x 4k)
• Multi-GPU technology
• Four modes of operation:
_o Alternate Frame Rendering (maximum performance)
_o Supertiling (optimal load-balancing)
_o Scissor (compatibility)
_o Super AA 8x/10x/12x/14x (maximum image quality)
_o Program compliant

Avivo Video and Display Engine
• High performance programmable video processor
_o Accelerated MPEG-2, MPEG-4, DivX, WMV9, VC-1, and H.264 decoding (including DVD/HD-DVD/Blu-ray playback), encoding & transcoding
_o DXVA support
_o De-blocking and noise reduction filtering
_o Motion compensation, IDCT, DCT and color space conversion
_o Vector adaptive per-pixel de-interlacing
_o 3:2 pulldown (frame rate conversion)
• Seamless integration of pixel shaders with video in real time
• HDR tone mapping acceleration
_o Maps any input format to 10 bit per channel output
• Flexible display support
_o Dual integrated dual-link DVI transmitters
_o DVI 1.0 / HDMI compliant and HDCP ready
_o Dual integrated 10 bit per channel 400 MHz DACs
_o 16 bit per channel floating point HDR and 10 bit per channel DVI output
_o Programmable piecewise linear gamma correction, color correction, and color space conversion (10 bits per color)
_o Complete, independent color controls and video overlays for each display
_o High quality pre- and post-scaling engines, with underscan support for all outputs
_o Content-adaptive de-flicker filtering for interlaced displays
_o Xilleon™ TV encoder for high quality analog output
_o YPrPb component output for direct drive of HDTV displays
_o Spatial/temporal dithering enables 10-bit color quality on 8-bit and 6-bit displays
_o Fast, glitch-free mode switching
_o VGA mode support on all outputs
• Compatible with ATI TV/Video encoder products, including Theater 550

ATI Graphics x 2

A lot of things had to happen before ATI was able to release CrossFire into the wild. ATI needed to design and implement the compositing engine, because the necessary logic was not present in the X800 and X1K family of GPUs. They had ensure compatible motherboards were available, and among numerous other things, they also had to engineer the software to enable the technology. We've covered much of what went into CrossFire over the past year, so we won't re-hash anything again here. But if you're not completely familiar with ATI's multi-GPU strategy, we recommend taking a look at these recent articles. There is a multitude of background information that laid the foundation for what we're going to showcase here today.

The ATI Cross Fire solution we'll be spotlighting in this article consists of the following three main components, an ATI CrossFire Edition "master" Radeon X1800 XT card, an ATI Radeon Xpress 200 CrossFire Edition chipset based reference design motherboard, and a second ATI Radeon X1800 XT standard graphics card.  And because the Radeon X1800 XT Master card will also work in conjunction with the Radeon X1800 XL, we've paired them together for some benchmarking as well.  We've actually covered all of these platform technologies in previous HotHardware articles linked above.

In our first "hands-on" look at ATI's Radeon X850 XT CrossFire configuration, we mentioned that CrossFire, like SLI, was a proprietary solution that required an ATI chipset-based motherboard, along with the requisite graphics cards, to function.  This situation has changed since the initial release, however.  Unlike NVIDIA's SLI, which is still a completely proprietary solution that "officially" requires two matched GeForce cards and an nForce 4 SLI chipset-based motherboard, CrossFire will now function on compatible Intel Chipsets as well.  And there are no limitations in hardware that'll prevent CrossFire from working on other chipsets either, provided they've got the proper slots and PCI Express implementations.

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