More ATI Radeon HD 2600 and HD 2400 Details Unveiled
 

AMD and add-in board partners will offer a variety of ATI Radeon HD 2600-based graphics cards. The different models include variations with GDDR4, GDDR3 and DDR2 memory in 512MB or 256MB configurations with or without video input and output capabilities.

Catering towards value users is the ATI Radeon HD 2400 with its 40 stream processors. Two SIMDs and one texture unit join the 40 stream processors. AMD plans to offer the ATI Radeon HD 2400 in Pro and LE models with varying configurations

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Why a DDR version? Lower cost?

Yes, DDR2 is cheaper than DDR these days, and it would also usually work out to be cheaper than GDDR3.