What makes DDR separate from SDRAM is that DDR can transfer memory on both the rise and the fall of a clock cycle.

There are currently 4 types of DDR memory available.

1. PC1600 DDR provides a 1.6GB/second throughput of data.
2. PC2100 DDR, provides a 2.1GB/second throughput of data.
3. PC2700 DDR, provides a 2.7GB/second throughput of data
4 PC3200 DDR , provides a 3.2GB/second throughput of data