ATI has been on a role lately coming back strong with their 3000 series and excellent chipsets that have been a bright spot for AMD. Their recent 4000 series may not have taken the best performance spot but easily captured the best price/performance ratios and made Nvidia drastically cut their prices. All of that isn't enough though as they are back with the much talked about ATI Radeon HD 4870 X2 which at last takes the single board GPU throne from Nvidia.

As with the 3870X2 and Nvidia's other dual GPU options the ATI Radeon 4870 X2 is two 4870s and as with the 3870 X2 are featured on the same PCB. This makes for a whopping 1600 stream processors but ATI have also gone further and bumped up the memory to 1GB GDDR5 per card standard bringing the total to 2GB of GDDR5 memory onboard which should easily handle resolutions of 1920x1200 and above with 8x anti-aliasing. As you'll see in our tests this extra RAM comes in handy and beats out two 4870s in Crossfire at the highest settings and resolutions.  The 4870 X2 also does a better job communicating between the two GPUs with much more bandwidth available and unlike the 3870X2 uses a PCIe 2.0 switch. When those moments kick in where the card really needs the extra bandwidth this will certainly come in handy. The card is long and features a massive heatsink as you'd expect on a card like this but isn't larger than Nvidia's latest cards and is actually the same length as a regular 4870.

All of the same great features of the Radeon 4000 series are here including UVD2 for better decoding of HD content, CrossfireX for 4 GPUs, DirectX 10.1 support, AVIVO, and 7.1 audio through HDMI. The card comes clocked in at 750MHz for the core and GDDR5 memory running at 1.8GHz. The Radeon 4870 X2 will retail for $549 but as always expect prices to drop in retail.

Something else we can speak about is that AMD is also planning an ATI Radeon HD 4850X2 card due out before the end of the month featuring what else but two 4850s on one PCB although with 2GB of GDDR3 memory instead of GDDR5 as with your normal 4850. This should still be an amazing beast of a card and should be launched at a very nice $399 price. It'll be interesting to see how the two cards stack up but this could be the card of choice for many.

Here are the technical specs of the 4870 X2.

• Unified Video Decoder 2 (UVD 2) for Blu-ray™ and HD Video
• Accelerated Video Transcoding (AVT)
• DVD Upscaling
• Dynamic Contrast
• Built-in HDMI with 7.1 surround sound support
• Integrated DisplayPort²

1.912 billion processors (956 million transistors per GPU on 55nm fabrication process)
PCI Express® 2.0 x16 bus interface
512-bit GDDR3 memory interface (ATI Radeon™ HD 4850 X2)
512-bit GDDR5 memory interface (ATI Radeon™ HD 4870 X2)
Microsoft® DirectX® 10.1 support

* Shader Model 4.1
* 32-bit floating point texture filtering
* Indexed cube map arrays
* Independent blend modes per render target
* Pixel coverage sample masking
* Read/write multi-sample surfaces with shaders
* Gather4 texture fetching

Unified Superscalar Shader Architecture

* 1600 stream processing units
o Dynamic load balancing and resource allocation for vertex, geometry, and pixel shaders
o Common instruction set and texture unit access supported for all types of shaders
o Dedicated branch execution units and texture address processors
* 128-bit floating point precision for all operations
* Command processor for reduced CPU overhead
* Shader instruction and constant caches
* Up to 320 texture fetches per clock cycle
* Up to 128 textures per pixel
* Fully associative multi-level texture cache design
* DXTC and 3Dc+ texture compression
* High resolution texture support (up to 8192 x 8192)
* Fully associative texture Z/stencil cache designs
* Double-sided hierarchical Z/stencil buffer
* Early Z test and Fast Z Clear
* Lossless Z & stencil compression (up to 128:1)
* Lossless color compression (up to 8:1)
* 8 render targets (MRTs) with anti-aliasing support
* Physics processing support

Dynamic Geometry Acceleration

* High performance vertex cache
* Programmable tessellation unit
* Accelerated geometry shader path for geometry amplification
* Memory read/write cache for superior stream output performance

Anti-Aliasing Features

* Multi-sample anti-aliasing (2, 4 or 8 samples per pixel)
* Up to 24x Custom Filter Anti-Aliasing (CFAA) for superior quality
* Adaptive super-sampling and multi-sampling
* Gamma correct
* Super AA (ATI CrossFireX™ configurations only)
* All anti-aliasing features compatible with HDR rendering

Texture Filtering Features

* 2x/4x/8x/16x high quality adaptive anisotropic filtering modes (up to 128 taps per pixel)
* 128-bit floating point HDR texture filtering
* sRGB filtering (gamma/degamma)
* Percentage Closer Filtering (PCF)
* Depth & stencil texture (DST) format support
* Shared exponent HDR (RGBE 9:9:9:5) texture format support
 

Let's move onto our test system specs and benchmarks