Neoseeker has published a review of the ATI X1950XTX video card

While a new cooler may not in itself be enough to herald a new SKU, the addition of newer memory running at significantly faster speeds evidently is. The X1950 XTX uses 512 MB of brand new GDDR4 memory and is the first graphics card yet to ship with this new memory. The focus of GDDR4 is increased bandwidth (at the expense of latency however) and lower power consumption and has been tested running at speeds up to 3.2 GHz DDR. Being the first product to market with the new technology, ATI have not pushed the envelope that far but still manage a whopping 2.0 GHz representing the fastest memory clocks of any shipping graphics card yet.

ATI X1950XTX Review