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DDR2 Memory Overview

Tuesday, October 5, 2004
DDR2 is the next-generation DDR memory technology which features faster speeds, higher data bandwidths, lower power consumption, and enhanced thermal performance.

In Q3 of 2004, DDR2 memory will be offered on most desktops, servers, notebooks, telecommunications/networking and other PC platforms in the following form-factors:
DDR2 Unbuffered DIMM ECC and Non-ECC ( 240pin)
For PC and low end workstations
Dimension approx. 5.25" x 1.18" (13.34cm x 2.99cm)

Registered ECC DIMMs ( 240 pin) 

For Server and high end workstations

Unbuffered DDR2 SODIMM ( 200pin)

For Laptop and Cube PC

MicroDIMM( 214 pin)

Micro-DIMM is a SO-DIMM with a smaller outline and thickness than standard SO-DIMMs. Therefore it is designed for sub-Notebooks applications which are mobile type, slim type and super light weight Notebooks.

  • Very small outline DIMM
  • Speed: DDR2-400, DDR2-533
  • Densities: 256MB, 512MB, 1GB
  • Based on Infineon's 512Mbit and 1Gb components

    What is a DDR2 DIMM ?
    A dual inline memory module (DIMM) consists of a number of memory components (usually black) that are attached to a printed circuit board (usually green). The gold pins on the bottom of the DIMM provide a connection between the module and a socket on a larger printed circuit board. The pins on the front and back of a DIMM are not connected to each other.
    DDR2 memory modules are offered in two frequency range, 400MHz and 533MHz speeds (data rate) in 2004, and followed by 667MHz by Fall of 2005.
    240-pin DIMMs are used to provide DDR2 SDRAM memory for desktop computers. Each 240-pin DIMM provides a 64-bit data path (72-bit for ECC or registered modules), so they are installed singly in 64-bit systems. Most DDR2 chipsets are expected to support dual-channel memory, effectively providing a 128-bit data path

    DDR2 DIMM memory modules are not backward-compatible with DDR DIMM , due to incompatible pin configurations, core voltage, and memory chip technology. DDR2 modules are designed with a different "key" in the edge connector to prevent insertion into incompatible memory sockets such as DDR motherboard. A DDR2 SDRAM DIMM will not fit into a standard SDRAM DIMM socket or a DDR DIMM socket. DDR2 modules use a 1.8V power supply, providing a big power saving over the 2.5V DDR modules.
    240-pin DIMMs are available in DDR2 PC2-4200 (DDR2-533) SDRAM or DDR2 PC2-3200 (DDR2-400) SDRAM. To use DDR2 memory, your system motherboard must have 240-pin DIMM slots and a DDR2-enabled chipset.
    DDR2 Memory Chips

    DDR2 memory can no longer be made into TSOP chips, and are offered FBGA (Fine-pitch Ball Grid Array) chips.
    DDR FBGA 60 Ball from Elpida
    DDR TSOP 66pin from Samsung
     DDR2 memory chips main features are :
    • JEDEC standard Power Supply
    • VDD = VDDQ = 1.8V +/-0.1V
    • 4 internal memory banks (512Mb)
    •  8 internal memory banks (1Gb)
    • Programable CAS Latency 3,4 and 5
    • Programmable Additive Latency: 0,1,2,3 and 4
    • Write Latency = Read Latency -1
    • Programmable Burst Length: 4 and 8
    • Programable Sequential / Interleave Burst
    • OCD (Off-chip Driver Impedance Adjustment)
    • ODT (On-Die Termination)
    • 4 bit prefetch architecture
    • 1K page size for x4 & x8, 2K page size for x16
    • Data-Strobe: Bidirectional, Differential
    • Weak Strength Data-Output Driver Option
    • Auto-Refresh and Self-Refresh
    • Power Saving Power-Down modes
    • 7.8µs Maximum Average Periodic Refresh Interval
    • Package:
      60 pin FBGA for x4 & x8 components
      84 pin FBGA for x16 components.
    Memory Classifications
    Memory Speed are offered in 400, 533 & 667Mhz
    Memory Chip classification are named : DDR2-400 , DDR2-533Mhz and DDR2-667Mhz
    Module DIMM Classificiation are named : PC2-3200 or 400Mhz) , PC2-4200 or 533 mhz and PC2-533 or 667Mhz
    Module Bandwidth : PC2-3200 = 3.2 Gb/s , PC2-4200= 4.2 Gb/s & PC2-5300= 10.6 Gb/s

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

    Feature DDR DDR2 DDR2 Advantage
    Memory Package TSOP and BGA FBGA only Higher speed and improved electrical and thermal performance
    On Die Termination Memory signal terminated on motherboard In  chip Terminates memory signal in every chip to improve signal and integrity
    Voltage 2.5 volts 1.8 Volts Lower power consumption and heat dissipation
    Memory Chip Size 128Mb - 1Gb 256Mb-4Gb* 1Gb chip -> 2GB DIMM (no chip stacking)
    4Gb chip -> 8GB DIMM (no chip stacking)
    Frequency 200, 266, 333, 400 Mhz 400, 533, 667 Speed above 400MHz
    Module Bandwidth Up to 6.4GB/s Dual Channel Up to 10.6GB/s Highest memory performance

    DDR2 versus DDR Modules

    DDR2 memory modules have basically the same dimensions as the DDR modules, but have different pin configurations, therefore DDR2 DIMM will not fit in the DDR memory slot.

    The number of black components on a 240-pin DIMM may vary, but they always have 120 pins on the front and 120 pins on the back.While 240-pin DDR2 DIMMs, 184-pin DDR DIMMs and 168-pin DIMMs are approximately the same size, 240-pin DIMMs and 184-pin DIMMs have only one notch within the row of pins.

    The table compares the different types of modules for DDR and DDR2:

      DDR2 DDR
    Unbuffered DIMM 240pin 1.8V 184pin 2.5V
    Registered DIMM 240pin 1.8V 184pin 2.5V
    SODIMM 200pin 1.8V 200pin 2.5V
    Mini Registered DIMM 244pin 1.8V
    MicroDIMM 214pin 1.8V 172pin 2.5V

    Because of different voltages and pin configurations, DDR2 modules will have a different "key" or notch in their connector to prevent them from being plugged into an incompatible socket. DDR2 memory modules will only fit in systems and motherboards designed to specifically support DDR2 memory. 



  • By: DocMemory
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