This may have been posted a while ago however still an interesting read :
Rest here :http://www.xbitlabs.com/articles/vid...-gf7900gs.html
Cut-throat competition between ATI Technologies and Nvidia encouraged them not only to introduce new high-end graphics solutions every half a year, but sometimes to even completely update their entire product line-up. Of course, this state of things is very favorable for the end-users, because it ensures pretty rapid price drop for the new products as well as quick performance improvement in all market segments.
Since it is hardly profitable to develop two-three new GPUs every half a year, the leading GPU developers try to modify their GPUs so that they could last them a little bit longer. It means that each GPU will find its way into a wide variety of graphics products. So, the flagship solutions, like ATI R520 and Nvidia G71 can be found not only in$549+ graphics cards, but also in $199 solutions. However, the latter solutions can also be based on specifically developed low-cost GPUs.