DDR2 - Why Consider It?

Compared to DDR, DDR2 offers extraordinary performance, reduces power consumption, maximizes DRAM throughput, improves signal integrity, and optimizes flexibility. Some of the measurable differences are highlighted in the comparison chart below.

Feature/Option DDR DDR2 DDR2 Advantage
 Package  66-pin TSOP
 54-, 60-ball FBGA
 60-, 84-ball FBGA
 63-ball FBGA DDP
 Enables better electrical performance and speed, dual die package enables higher densities
 Voltage (core and I/O)

 Low volt


 Reduces memory system power demand

 DDR2 offers a low voltage solution
 Densities  256Mb to 1Gb  256Mb to 4Gb  High-density components enable large memory subsystems with fewer chip counts
 Internal banks  4  4 and 8  1Gb and higher density DDR2 devices have 8 banks for better performance
 Prefetch (MIN WRITE burst)  2  4  Enables faster clock rates
 Data rate (MT/s per pin)  333
 Migration to higher data bandwidth
 READ latency

 Additive latency (posted CAS)
 2, 2.5, 3 CLK

 CL + AL
 CL=3, 4, 5, 6, 7

 AL options
 0, 1, 2, 3, 4, 5, 6
 Eliminating one-half clock settings helps speed internal DRAM logic and simplify timing

 Mainly used in server applications to improve command bus efficiency
 WRITE latency  1 clock  READ latency - 1  Improves command bus efficiency
 DQ bus termination  Motherboard parallel to Vtt  DRAM on-die termination (ODT), optional on-motherboard termination  ODT for both memory and controller improves signaling, lowers power, and reduces system costs
 Data strobes  Single-ended  Differential or single-ended  Improves system timing margin by reducing strobe crosstalk
 Modules  184-pin DIMM
  • unbuffered
  • registered
 200-pin SODIMM
 240-pin SODIMM
  • unbuffered
  • registered
  • fully buffered
 200-pin SODIMM
 Improved layout, more form factors, and power delivery design