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McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


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(Synchronous DRAM) The type of dynamic RAM memory chip in wide use since the mid-1990s. SDRAM divides the chip into two cell blocks and interleaves 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) Since 2000
DDR SDRAM doubled the data transfer rate by using both the rising and falling edges of the clock cycle, and more speed is achieved with each generation (see below).

Memory Channels
Motherboards may support one, two or four channels. More than one channel requires installing modules in a prescribed order (see image below). See GDDR.

        Clock    Transfer        DIMM        Speed      Rate         Module DDR    (MHz)     (MT/s)    (V)  Pins

 DDR5 1600-3200  3200-6400  1.1  288
 DDR4  800-1600  1600-3200  1.2  284
 DDR3  400-1200   800-2400  1.5  240
 DDR2  200-533    533-800   1.8  240
 DDR   100-200    200-400   2.5  184
 SDRAM  66-133     66-133   3.3  168

Matched Slots for Dual Channel
Dual-channel motherboards use color-coded sockets so that DDR memory modules are inserted in pairs. This motherboard supports two pairs of DIMM modules (see memory module).

DDR RAM Modules Are "Keyed"
This example shows the notching of three DDR generations. Modules and slots are "keyed" to prevent the wrong DDR version from being inserted. See memory module.

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 billions of bits. (Image courtesy of The MITRE Corporation Archives.)
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References in periodicals archive ?
Accompanying the SoC is 1GB of 533MHz DDR2 SDRAM. The tablet has a 6-inch screen with a resolution of 1280 x 720 pixels and weighs 160 grams.
According to the analysis by Teardown, the features of Google Glass include Android 4.0.4 Ice cream Sandwich operating system, 640 x 360 display screen, 570 mAh battery life, 5 MP camera, WiFi/Bluetooth, GPS, accelerometer, compass and gryoscope as its connectivity and sensor system, 16 GB NAND, 1 GB DDR2 SDRAM and Texas Instruments OMAP4430 processor.
* Up to 2 GB of DDR2 SDRAM memory, with an 800 MHz bus frequency.
Part number TMPV7506XBG TMPV7504XBG CPU core Toshiba original 32-bit RISC CPU Media Embedded Processor (MeP) Image recognition engine Toshiba original multi-core media processor "Venezia" (incorporating " MPE " x 4) Image processing accelerators Affine transform 1ch Filter 2ch Histogram 1ch Histogram of oriented gradient (HOG) 1ch - Matching 1ch On-chip ROM/RAM Mask ROM: 64 Kbytes SRAM: 2080 Kbytes On-chip peripheral functions Video input I/F 4ch 2ch Video output I/F 1ch Main memory controllers DDR2 SDRAM controller NOR Flash/SRAM controller PCI Express 1 lane - CAN controller 3ch I2C I/F 4ch UART I/F 5ch SPI I/F 4ch PCM I/F 2ch Timer 11ch Power supply voltage Core: 1.1 V, I/O: 3.3 V and 1.8 V Operating frequency Max.
Although the FTC found that Rambus had acquired monopoly power as a result of its failure to disclose its intellectual property holdings when JEDEC was adopting its initial SDRAM and DDR SDRAM standards, and thus would have required Rambus to reduce its royalties on those technologies, it concluded that "[t]he record does not support a finding that lock-in conferred durable monopoly power over DDR2 SDRAM by 2000." (58) In contrast, the EC obtained commitments from Rambus to cap royalty rates on subsequent versions of its technologies.
In addition to the 512Mb DDR SDRAM product family, ISSI offers SDR, DDR, mobile SDR/DDR, and DDR2 SDRAM product families in a variety of densities, organizations, and temperature ranges as well as a complete line of SRAMs targeted for automotive, networking, telecom, industrial and consumer applications.
The Opal Kelly XEM6110 measures 75 mm x 50 mm and features a Xilinx Spartan-6, 1 Gb (64M x 16 bit) DDR2 SDRAM, high-efficiency switching power supplies, two high-density 0.8-mm expansion connectors, and a low-jitter 100-MHz oscillator.
Relevant experimental data for these effects can be found in (Borucki et al., 2008; Borucki et al., 2007) where DDR and DDR2 SDRAM memories are studied.
1 GByte of DDR2 SDRAM is soldered to the board for optimum reliability.
The Mac mini, which has a suggested retail price of USD699, comes standard with a 2.4GHz Intel Core 2 Duo processor with 3MB of shared L2 cache, 2GB of DDR2 SDRAM, expandable up to 8GB, a DVD optical drive and a 320GB Serial ATA hard drive.