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DDR2 Advantages over DDR

DDR memory technology has matured and reached its limitations at 400MHz, the fastest speed that DDR memory is expected to support in high-volume.

The limitations impacting DDR400 are shown in the following table:

DDR400 Limitation Platforms Impacted Why
High power consumption Notebook Servers - Reduces notebook battery life
- Impacts servers with high memory content
High heat dissipation All - Excessive heat causes reliability problems
- More active cooling required
Memory "loading" Servers - Won't reliably support more than 2 dual-rank* DDR333/400 DIMMs per channel
No memory-chip stacking Servers - High-capacity modules using 1Gb DRAM chips are very expensive vs. stacked 2x512Mb; 400MHz DDR chips cannot be stacked like slower DDR266/200 chips.
400MHz limit All - Yields of DDR chips in excess of 400MHz are too low for high-volume production
* DDR2 will also support chip- or die-level stacking for high capacity server modules.


DDR2 was designed to overcome many of the problems with DDR:

Feature DDR DDR2 DDR2 Advantage
Memory Chip Package TSOP and BGA FBGA only Higher speed and improved electrical/thermal performance
On Die Termination (Memory signal terminated on motherboard) In every chip Terminates memory signal in every chip to improve signal quality and integrity
Voltage 2.5 Volts 1.8 Volts Lower power consumption and heat
Memory Chip Sizes 128Mb - 1Gb 256Mb-4Gb* 1Gb chip -> 2GB DIMM (no chip stacking)
4Gb chip -> 8GB DIMM (no chip stacking)
Speeds (MHz) 200, 266, 333, 400 400, 533, 667, 800 Speed limit raised above 400MHz
Module Bandwidth Up to 6.4GB/s
(dual-channel)		 Up to 12.8 GB/s
(dual-channel)		 Higher memory performance



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