DDR2 to DDR3

DDR3 – How Does It Compare to DDR2?

Next-generation, high-performance DDR3 pushes the envelope in key areas like power consumption, signaling speeds, and bandwidth and brings new levels of performance to desktop, notebook, and server computing applications. Below is a snapshot of how DDR3 stacks up against DDR2.

Feature/Option DDR2 DDR3 DDR3 Advantage
 Voltage (core and I/O)  1.8V  1.5V  Reduces memory system power demand
 Standard Low Voltage Option  No  Yes (1.35V)  Offers low-voltage DDR2 that matches standard DDR3 at 1.5V
 Densities (Production)  256Mb to 4Gb  1Gb to 4Gb  High-density components enable large memory subsystems with fewer chip counts
 Prefetch (MIN WRITE burst)  4-bit  8-bit  Reduced core speed dependency for better yield
 tCK - DLL enabled  125 Mhz to 400 Mhz  300 Mhz to 800 Mhz  Supports higher data rates
 Data rate (MT/s per pin)  533, 667, 800 Mb/s  800,1066,1333,1600 Mb/s  Migration to higher data bandwidth
 Burst length (BL)  BL4, BL8  BC4, BL8  BC4 provides relief from some "BL8" requirements
 Burst type  Fixed, via LMR  (1) Fixed, via MRS
(2) OTF, "on-the-fly"
 OTF allows switching between BC4 and BL8 without MRS command
 Data strobes  Differential or single-ended  Differential only  Improves system timing margin by reducing strobe crosstalk
 ODT (On Die   Termination)  RTT: 50, 75, 150 ohm  RTT: 20,30,40,60,120 Ohm  More ODT options improves signal fidelity and supports higher data rates
 Dynamic ODT  None  120, 60 Ohm  Improved signaling in multiple slots; pin reduction in point to point applications
 DQ Driver Impedance  18 Ohm  34 Ohm  Optimized for 2-slot and point to point systems
 Drive / ODT Calibration  None  External resistor  Improves accuracy over voltage and temperature
 Multi-purpose register (MPR)  None  Four Registers - 1 defined 3 RFU  Supports read calibration
 Write Leveling  None  DQS captures CK, DQ
drives out CK's state
 De-skews fly-by layout used by modules
 Modules

 240-pin SODIMM (unbuffered, registered, fully buffered)

 200-pin SODIMM

 240-pin UDIMM; RDIMM, FBDIMM tbd;
 204-pin SODIMM
 Improved layout, more form factors, and power delivery design; DDR3 also uses fly-by architecture
 Chipset support  Legacy  Latest  Newer chipset features
 Additive Latency  Yes  Yes  Tracks with CAS latency
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