DDR DIMM Memory Modules


Double Data Rate DIMM

Double Data Rate DIMM [DDR-DIMM, DDR DIMM, or DDR1] utilizes the JEDEC standard for Double Date Rate [DDR I] SDRAM. This page covers the DDR memory modules, which may also be found as SO-DIMM, and Micro-DIMM module formats. DDR DIMM modules are produced in two different flavors; registered or unbuffered. Registered DIMMs have their address and control lines buffered on the DIMM to reduce signal loading. Because the Registered DIMM requires a buffer they are more expensive then unbuffered DIMMs. Unbuffered DIMMs do not buffer the address lines and control lines, so they cost less and may be limited in the amount the system may have installed because of system loading. How ever an unbuffered DDR DIMM is able to operate one clock cycle faster then a registered DIMM.

In addition to the DDR1 DIMM module being registered or unbuffered, the physical size of the module may also vary between DIMM, SODIMM, or Mirco-DIMM. The SO-DIMM and Micro-DIMM formats are used in lap-top computers, while the standard DIMM format is used in desk-tops and work-stations.

Refer to the general Memory Module page for a more complete listing of different types of modules, manufactures and descriptions. DDR modules may be purchased in one of the following speed grades:

...DDR SDRAM:....Double Data Rate SDRAM [DDR200, DDR266, DDR333 are standard]
.........PC1600 (DDR-200 SDRAM); Clock Speed: 100MHz, Data Rate: 200MHz, Through-put 1600MB/s
.........PC2100 (DDR-266 SDRAM); Clock Speed: 133MHz, Data Rate: 266MHz, Through-put 2100MB/s
.........PC2400 (DDR-300 SDRAM); Clock Speed: 150MHz, Data Rate: 300MHz, Through-put 2400MB/s
.........PC2700 (DDR-333 SDRAM); Clock Speed: 166MHz, Data Rate: 333MHz, Through-put 2600MB/s
.........PC3000 (DDR-366 SDRAM); Clock Speed: 183MHz, Data Rate: 366MHz, Through-put 2900MB/s
.........PC3200 (DDR-400 SDRAM); Clock Speed: 200MHz, Data Rate: 400MHz, Through-put 3200MB/s

As the name implies, Double Data Rate interfaces provides two data transfers per clock. The clock is differential. The data is registered when the CK goes high [the + side], and /CK goes low [the - side].
The first generation of DDR memory DDR1 is being replaced by DDR2, or DDR3.

DDR Electrical Interface

Double Data Rate IC's use 2.5 volt SSTL_2 compatible I/O [class II], how ever the supply voltage may be higher. The main supply voltage [VDD] is 3.3v or 2.5v for DDR 200, DDR266, and DDR333, while 2.6v for DDR400. The output drive supply [VDDQ] is 3.3v or 2.5v for DDR200, DDR266, and DDR333, while it's 2.6v for DDR400. DDR uses a bi-directional data strobe to indicate valid data [DQS].
SSTL-2: Stub Series Terminated Logic for 2.5v [JESD8-9]. Class II provides for higher power dissipation, Higher drive and a maximum current of 15.2mA. DDR, Double Data Rate. [JESD79] defines two data transfers per clock cycle. The Clocks are differential. Power Supply [VDD = 3.3v + 0.3v or 2.5v + 0.02v for DDR 200, DDR 266, or DRR 333; and 2.6v + 0.1v for DDR 400]. Inputs and outputs are compatible with SSTL_2. These DIMMs are 184 Pin in size and are not interchangeable with older 168-pin SDRAM modules.

DDR DIMM SSTL2 Voltage Levels, I/O Switching Levels
SSTL Switching Levels

DDR memory voltage regulator manufacturers are listed on the DDR Voltage Regulators page.

DDR DIMM Manufacturers

DDR memory modules are found in desk tops, workstations, and Server applications. Three form factors of DDR are available:
184-pin DDR DIMM [Desk-Top computers]
200-pin DDR SODIMM [Notebook computers]
172-pin DDR MicroDIMM [Notebook computers]

Apacer Inc {184-Pin 2.5v DDR, ECC/Non-ECC PC2100, PC2700, PC3200, PC4000. 256MB to 1GB memory modules}

Centon Electronics {184-pin Registered/Unbuffered DIMM, 200-pin SODIMM, 172-pin MicroDIMM. SDRAM, 168-pin Registered/Unbuffered DIMM / 144-pin SODIMM/MicroDIMM}

Century Microelectronics Inc. {DDR PC2100 DIMM Memory Module Manufacturer}

Corsair {PC2100, PC2700, PC3200 DDR SDRAM Module}

Integrated Device Technology, Inc. 'IDT' {memory Module Support; Zero-Delay PLL Clock Drivers, SSTU Registers, 1:10 PLL Clock Driver}

Infineon {DDR/DDR2 SDRAM Memory Modules-Unbuffered DIMM, Registered DIMM, Fully-Buffered DIMM, SO-DIMM, Micro-DIMM}

Kingmax Inc. {DDR 400MHz (PC-3200) SDRAM Module}

Kingston Technology {All DDR Speeds, DDR2 PC3200/PC4200, SDRAM PC133/PC100MHz, Many Flash types}


Microsemi {DDR2 Modules, DDR Modules, SDRAM Modules, SSRAM, SRAM Modules, Flash Memory Modules}

Nanya Technology Corp. {SDRAM Memory- DDR SDRAM Memory}


OCZ Technology Inc {DDR2 PC25400/4200, DDR PC2700/3200/3500/4200, Dual Channel}

PNY Technologies {Desktop/Notebook SDRAM / DDR, PC4000 DDR500, PC3700 DDR466}

Samsung Semiconductor Inc. {SDRAM-DDR SDRAM-RAMbus DRAM-EDO Fast page DRAM}

SMART Modular Technologies {DDR SDRAM Memory Modules, FB-DIMM, DDR SODIMM, DDR2 Mini DIMM, PC133 SDRAM, DRAM, SRAM}

Toshiba America Electronic Components Inc. {DIMM Memory Module Manufacturer}

Vanguard International Semiconductor 'VIS' {SDRAM / DRAM DIMMs - DRAM SIMM Manufacturer}

Viking Components {SDRAM PC66/PC100/PC133, Direct Rambus (DRDRAM) module, EDO and FPM DRAM module, SIMMs, DIMMs, SODIMMs}

Wintec Industries Inc. {DDR2 Modules, DDR Modules, SDRAM Modules, Rambus, EDO/FPM Modules}

Electronic Engineering Tags: DDR DIMM, SSTL, Integrated Circuit Bus, Chip-to-Chip Interface, Microcomputer Bus, Memory Busses, Peripheral chip.

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Modified 4/18/12
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