SDRAM

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SDRAM

[¦es¦dē′ram]

SDRAM

SDRAM

(Synchronous DRAM) The type of dynamic RAM memory chip that has been widely used since the mid-1990s. SDRAM eliminated wait states by dividing the chip into two cell blocks and interleaving data between them. While a bit in one block is accessed, a bit in the other is prepared for access. See dynamic RAM.

DDR (Double Data Rate)
In 2000, DDR SDRAM doubled the data transfer rate by using both the rising and falling edges of the clock cycle. The data rate of each DDR generation is faster than the previous with a six-fold increase from DDR1 to DDR4. In addition, less power is required (see table below). In order to prevent inserting the wrong DDR into the motherboard, DDR memory modules are keyed differently (for details, see memory module).

Channels
Chipsets on the motherboard may support one, two or four memory channels (triple channel has since come and gone). For example, mainstream motherboards support dual channel, which is why memory modules are generally installed in pairs. While data are being read or written to one memory module, the second module is being prepared for reading or writing. High-end motherboards support quad channel. See SGRAM.

MEMORY GENERATIONS

  Following are the most popular memory
  module speeds for each SDRAM generation.

       Memory Speed   DIMM   Voltage          (MHz)      Module  Required

  DDR4     2400     284-pin   1.2
  DDR4     2133     284-pin   1.2

  DDR3     1866     240-pin   1.35/1.5
  DDR3     1600     240-pin   1.35/1.5
  DDR3     1333     240-pin   1.35/1.5

  DDR2      800     240-pin   1.8/2.5

  DDR       400     184-pin   2.5

  SDRAM     133     168-pin   3.3
  SDRAM     100     168-pin   3.3


Matched Slots for Dual Channel
This motherboard uses colored sockets so that module pairs are inserted properly. It supports three pairs (one orange and two lavender). (Image courtesy of Giga-byte Technology Company Ltd., www.giga-byte.com)







A Little Nostalgia
These 12 bits of magnetic core memory from the Whirlwind computer of the early 1950s take up about a quarter of a square inch. Today, that much space holds hundreds of millions of bits. (Image courtesy of The MITRE Corporation Archives.)
References in periodicals archive ?
a slot-load 8x SuperDrive with double-layer support (DVD+R DL/DVD+/-RW/CD-RW); -- 512MB of PC2-4200 DDR2 SDRAM running at 333 MHz, expandable up to 2GB; -- 80GB Ultra ATA/100 (5400 rpm) hard drive with Sudden Motion Sensor; -- Built-in AirPort Extreme wireless networking & Bluetooth 2.
Elpida 512 Megabyte DDR2 SO-DIMMs (Part numbers: EBE52UD6AFSA-6E-E: PC2-5300, EBE52UD6AFSA-5C-E: PC2-4200, EBE52UD6AFSA-4A-E: PC2-3200) are available in three speed grades, DDR2-667 (CL=5-5-5), DDR2-533 (CL=4-4-4) and DDR2-400 (CL=3-3-3) respectively, and they are organized as 64M words x 64-bits x 2 Ranks.
announced today the launch of 2-Rank 8GB PC2-4200 RDIMM, featuring MetaRAM's MetaSDRAM[TM] technology.
512 MB 667 MHZ PC2-5300 FB-DIMM 1GB 667 MHZ PC2-5300 FB-DIMM 2GB 667 MHZ PC2-5300 FB-DIMM 512 MB 533 MHZ PC2-4200 FB-DIMM 1GB 533 MHZ PC2-4200 FB-DIMM 2 GB 533 MHZ PC2-4200 FB-DIMM
5 GB of PC2-4200 DDR2 memory, and robust graphics capabilities through the Intel Graphics Media Accelerator 900.
The unbuffered DDR2 PC2-4200 Memory Modules support data rate up to 533 MHz.
Features: iMac G5 - * Memory Size: 512-MB to 2-GB DDR2 (single module) * Memory Speed: PC2-4200 (533MHz) * Memory Type: Dual Channel DDR2 * Pins: 240 pin DIMM * Lifetime Warranty with 24/7 tech support PowerMac G5 - * Memory Size: 512-MB to 4-GB DDR2 (two module format) and 1-GB to 2-GB DDR2 with ECC (two module format) * Memory Speed: PC2-4200 (533MHz) * Memory Type: Dual Channel DDR2 / Dual Channel DDR2 with ECC * Pins: 240 pin DIMM * Lifetime Warranty with 24/7 tech support PowerBook (15" and 17" screen models) - * Memory Size: 512-MB to 1-GB DDR2 (single module) * Memory Speed: PC2-4200 (533MHz) * Memory Type: Dual Channel DDR2 * Pins: 200 pin S.
Latency Module Ranks x506472J30A-37A 512MB PC2-4200 533 64 Meg x 72 CL4-4-4 Single x506472J30A-50A 512MB PC2-3200 400 64 Meg x 72 CL3-3-3 Single x512872M30A-37A 1GB PC2-4200 533 128 Meg x 72 CL4-4-4 Single x512872M30A-50A 1GB PC2-3200 400 128 Meg x 72 CL3-3-3 Single x525672M30B-37A 2GB PC2-4200 533 256 Meg x 72 CL4-4-4 Dual x525672M30B-50A 2GB PC2-3200 400 256 Meg x 72 CL3-3-3 Dual
Dataram's DTM63303A, a PC2-4200 unbuffered 4-4-4 (latency) 512MB capacity module, is designed for Intel's new desktops, while its 512MB ECC version, DTM63304A, is designed for Intel workstations and one-way server architectures.
Densities of 256MB to 1GB for Unbuffered modules with ECC and 256MB to 1GB Unbuffered Non-ECC modules, as well as 256MB to 2GB densities of Registered DIMM modules at speeds of PC2-3200 and PC2-4200, are currently available in mass production quantities.