GDDR memory 
graphics double data rate memory 
GDDR is an evolving family of DDR SDRAM chips that are designed specifically to handle the enormous demands of graphics processing. Currently, three standards exist: GDDR-I, GDDR-II (backed by Nvidia), and GDDR-III (backed by ATI). The standards differ in their clock speed, bandwidth, and power-management capabilities, among other attributes. Most graphics card vendors (including ATI and Nvidia) are hedging their bets by planning for compatibility with whichever standard prevails.