http://www.techreport.com/onearticle.x/9742
Desai also pointed to the question of market share. NVIDIA sizes up the market by looking at past sales data for GPUs overall, and then draws up chip forecasts based on the share of that market it wants to capture. He claimed 7900 supply is on track with NVIDIA's forecasts, but cards are still difficult to keep in stock. Meanwhile, he suggested, the widespread availability of competing Radeon cards could be because the ATI products simply aren't selling very well in comparison. To bolster this argument, NVIDIA pointed out TigerDirect's top sellers list for video cards, which currently has the XFX GeForce 7900 GT at #3 and the Radeon X1900 XTX?the only ATI card in the top 10?at #6. NVIDIA suggested we check with online vendors to confirm the proportion of Radeon to GeForce sales.
We weren't able to get any e-tailers to go on record with proportional sales data on ATI and NVIDIA cards, but we did get a clear sense that the picture NVIDIA painted of the situation is fairly accurate. GeForce 7900 cards are outselling the ATI-based competition by well over four-to-one ratios at some online vendors, amazingly enough. The supply is substantial, too: shipments of 7900 cards are arriving on palettes and selling out within the space of a day or two?sometimes less. Vendors are not satisfied with the volumes of cards they are getting, of course; they would like more. But this is not a simple case of extended, persistent lack of product from NVIDIA and stellar supply from ATI. NVIDIA appears to be moving many more high-end GeForces through e-tail than ATI is high-end Radeons