Read closer I said X1900XTX to X1950XT. They launched it as a totally new product, even renamed the core R580+ when it was the same R580 core that didn't even go through a die shrink. So it is nothing like the relation between 8800GTX and 8800Ultra.
Give me a little more credit than to assume I don't know the relationship between X1900XT and X1900XTX... Do I seem like the kind of person that wouldn't understand that relationship?
What are you talking about ? the X1950XTX was just a new variant of the X1900XTX, with 512mb of GDDR4 ( first gpu to use GDDR4), when the X1900 series was just using GDDR3 ... It was nothing more or less and this why they had call it X19
50XTX .... you call that renaming ? , they have never advertise it like a "completely new architecture or gpu", this was just a power variant of the X1900XTX . they can have call it differently X1900GTX Pro ... they have decide to call it X1950XTX.... where this name is a problem for you... i have never seen one person in hardware sites, reviews forums, who have say it's a problem to have call it X19500XTX...
And for the R580+, it's just cause the memory controller was not the same, ofc they was need a memory controller and buffers who can support the GDDR4 ..... for recall the X1900 series should have normally come with GDDR4 support, but Samsung have not finalize the process of production, so during developpement, ATI had go back to GDDR3, during this time Samsung have finnally sort up their problem, and AMD have decide to launch anyway this version of the X1900XTX...