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tweet on NVIDIA's Twitter account reveals that the company's first DirectX 11 compliant consumer graphics products will be named GeForce GTX 480 and GeForce GTX 470, against popular opinion that they could make for the GeForce GTX 300 series. The most likely reason for this could be that the company has released mobile graphics products under the GeForce GT 3xx series which are based on its GT21x series GPUs which are DirectX 10.1 compliant. It would be hence easier to make out that DirectX 11 products start in the 400 series.
The two are based on NVIDIA's GF100 GPU which physically has 512 CUDA cores (shader units), a 384-bit wide GDDR5 memory interface, and DirectX 11 compliance. While the GTX 480 is likely the full-featured part, it remains to be seen how NVIDIA carves out the GTX 470 SKU. An enquiry by AnandTech confirmed the authenticity of the Twitter account.
Source: AnandTech