Samsung announced that its GDDR4 (Graphics Double Data Rate, version 4) high-speed graphics memory chip is being used in both the 1GB ATI Radeon HD 2900 XT and the 256MB ATI Radeon HD 2600 XT graphics processing cards.

The 1GB card has the widest bus in the industry designed for full-performance, high dynamic range (HDR) rendering in PCs. "We chose Samsung’s GDDR4 memory for our 1GB ATI Radeon HD 2900 XT and ATI Radeon HD 2600 XT graphics cards because its design complements our strategy in offering leading-edge technology to a broader enthusiast gaming market,” said Vijay Sharma, Director, Product Marketing, AMD Graphics Products Group. “We’re committed to working with key players in the industry like Samsung to develop advancements that work to continuously improve past solutions."

Samsung’s GDDR4 memory devices are now in mass production at the 512Mb density level. Samsung developed the world first GDDR4 device last year and submitted a paper on a 4Gbps GDDR4 at the International Solid State Circuits Conference (ISSCC) earlier this year.
Via this Samsung press-release.