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Onboard Crossfire with R700

Radeon HD 4870 X2 reviewed

AMD attacks Nvidia's Geforce GTX 200 series once again. This time they are aiming for the flagship Geforce GTX 280. Our review reveals if the card can reach the top position.

Radeon HD 4870 X2 reviewed
 
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AMD's launch policy is quite odd at the moment. With the release of the Radeon HD 4850 the press was not allowed to present full reviews: benchmarks yes, details about the architecture no. The same deal for the HD 4870 X2. We are allowed to publish some benchmarks and impressions while details about the architecture are an absolute no-go. But that can't keep us from interpreting the results.

Radeon HD 4870 X2: Powered by two hearts
Radeon HD 4870 X2 reviewed
 
[Source: view picture gallery]

Radeon HD 4870 X2 reviewed
 
[Source: view picture gallery]
The Radeon HD 4870 X2 is equipped with two RV770 chips that cooperate via the Crossfire X technology. You might have asked yourself why AMD and Nvidia do use this approach over and over again. The reason for this is an economical one: It is much cheaper to develop and produce a small graphics chip. Every additional transistor requires more know-how and needs more space on the wafer. Furthermore with a growing size of the GPU, the number of malfunctions rises. While Nvidia took the risk with the GT200, the financially stricken Canadians chose the performance of multiple chips. Ex-champion 3dfx did something quite similar with the Voodoo 5 series about eight years ago. But today more GPUs don't automatically result in a better gaming performance.

Radeon HD 4870 X2 reviewed
 
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The RV770 duo on the HD 4870 X2 is called R700 by AMD. For communication of the GPUs there is a PLX bridge chip. The new chip (PEX86BB-AA50BC F) is compatible with PCI Express 2.0 and that grants an improved data throughput.

Radeon HD 4870 X2 reviewed
 
[Source: view picture gallery]
The board is 27 centimeters long, just the same as the Geforce GTX 280. The cooler is equally long and almost covers all of the PCB. This time AMD uses copper to for the GPU blocks - for the HD 3870 X2 they used aluminum. If you think of the 160 watt TDP of the HD 4870, you might predict this solution really is necessary to have the 4870 X2 run stable. The PLX chip consumes less than 1 watt and therefore a thermal pad suffices for the connection to the cooler. The overall weight of the cooler is 1,080 grams.

The clock speeds fully match those of the HD 4870: Both GPUs run with 750 Megahertz and the GDDR5 VRAM is working with 1,800 Megahertz. 16 chips with 128 MiByte each are placed on the board and deliver an overall capacity of 2,048 MiByte. Yes that's right: Two Gigabyte video memory. Each chip can fully access 1,024 MiByte - rumors about a combined memory pool are wrong.




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Author: Vötter, Sauter (Jul 25, 2008)






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