(Synchronous DRAM) A type of dynamic RAM (DRAM) memory chip that has been widely used since the late 1990s. SDRAM chips 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.
Double Data Rate (DDR)
DDR SDRAM doubles transfer rates by transferring data on both the rising and falling edges of the clock. DDR uses a 184-pin DIMM module in contrast to the 168-pin DIMM of earlier SDRAMs. Laptops use 200-pin SODIMM modules.
DDR2 and DDR3
DDR2 chips increase data rates using various techniques such as on-die termination, which places the terminating transistors that eliminate excess signal noise on the chip itself. DDR3 offers a moderate speed improvement over DDR2, owing to 90 nm fabrication (see feature size).
DDR2 and DDR3 use 240-pin DIMM modules. DDR, DDR2 and DDR3 modules are all keyed differently so that they cannot be inserted into the wrong motherboard slots.
Dual Channel
Chipsets on the motherboard may support two independent memory controllers, which allow access to two memory modules simultaneously (upstream data on one 64-bit channel; downstream data on the other). Channels can be configured as two 64-bit or one 128-bit. Modules must be installed in matched pairs unless the chipset has an option for mismatched modules. See memory module and SGRAM.
In the following list, the single channel speeds are given. If dual channel is implemented, the memory speed and data rates are doubled, and many memory products use the doubled rate in their chip designations.
Matched Slots for Dual Channel
Motherboards that support dual channel use color coded memory slots so that module pairs are inserted properly. This example shows three pairs (one orange and two lavender). (Image courtesy of Giga-byte Technology Company Ltd., www.giga-byte.com)
A Little Nostalgia
This is 12 bits of magnetic core memory from the Whirlwind computer of the early 1950s and is about a quarter inch square in size. Today, that much space holds hundreds of millions of bits. (Image courtesy of The MITRE Corporation Archives.)
Double Data Rate (DDR)
DDR SDRAM doubles transfer rates by transferring data on both the rising and falling edges of the clock. DDR uses a 184-pin DIMM module in contrast to the 168-pin DIMM of earlier SDRAMs. Laptops use 200-pin SODIMM modules.
DDR2 and DDR3
DDR2 chips increase data rates using various techniques such as on-die termination, which places the terminating transistors that eliminate excess signal noise on the chip itself. DDR3 offers a moderate speed improvement over DDR2, owing to 90 nm fabrication (see feature size).
DDR2 and DDR3 use 240-pin DIMM modules. DDR, DDR2 and DDR3 modules are all keyed differently so that they cannot be inserted into the wrong motherboard slots.
Dual Channel
Chipsets on the motherboard may support two independent memory controllers, which allow access to two memory modules simultaneously (upstream data on one 64-bit channel; downstream data on the other). Channels can be configured as two 64-bit or one 128-bit. Modules must be installed in matched pairs unless the chipset has an option for mismatched modules. See memory module and SGRAM.
In the following list, the single channel speeds are given. If dual channel is implemented, the memory speed and data rates are doubled, and many memory products use the doubled rate in their chip designations.
Single
Channel Single
Memory Channel DIMM
Type Speed Symbol Data Rate Module
DDR3 800 MHz PC3-12800 12.8 GB/sec 240-pin
DDR3 667 MHz PC3-10600 10.6 GB/sec 240-pin
DDR3 533 MHz PC3-8500 8.5 GB/sec 240-pin
DDR3 400 MHz PC3-6400 6.4 GB/sec 240-pin
DDR2 533 MHz PC2-8500 8.5 GB/sec 240-pin
DDR2 500 MHz PC2-8000 8.0 GB/sec 240-pin
DDR2 400 MHz PC2-6400 6.4 GB/sec 240-pin
DDR2 375 MHz PC2-6000 6.0 GB/sec 240-pin
DDR2 333 MHz PC2-5300 5.3 GB/sec 240-pin
DDR2 266 MHz PC2-4200 4.2 GB/sec 240-pin
DDR2 200 MHz PC2-3200 3.2 GB/sec 240-pin
DDR 266 MHz PC-4200 4.2 GB/sec 184-pin
DDR 200 MHz PC-3200 3.2 GB/sec 184-pin
DDR 166 MHz PC-2700 2.7 GB/sec 184-pin
DDR 133 MHz PC-2100 2.1 GB/sec 184-pin
DDR 100 MHz PC-1600 1.6 GB/sec 184-pin
Single Channel
Speed
SDRAM 133 MHz 1.1 GB/sec 168-pin
SDRAM 100 MHz 800 MB/sec 168-pin
Matched Slots for Dual Channel
Motherboards that support dual channel use color coded memory slots so that module pairs are inserted properly. This example shows three pairs (one orange and two lavender). (Image courtesy of Giga-byte Technology Company Ltd., www.giga-byte.com)
A Little Nostalgia
This is 12 bits of magnetic core memory from the Whirlwind computer of the early 1950s and is about a quarter inch square in size. Today, that much space holds hundreds of millions of bits. (Image courtesy of The MITRE Corporation Archives.)
 | Reproduced with permission from Computer Desktop Encyclopedia. Copyright (c) 1981-2009 The Computer Language Company Inc. All rights reserved. |
Additional Resources
- HP Pavilion dv7-3065dx
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores. Any low-end desktop replacement must cut some corners on its way to providing a serviceable multimedia experience at an approachable price. At $729,...
- Product reviews 2009-11-25
- Gateway DX4300-11
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores.Gateway hasn't fared well with its most recent round of DX-series mainstream retail PCs. Neither the DX4300-03 nor the DX4822-01 received positive marks, and...
- Product reviews 2009-11-25
- Maingear Shift
- With its new Shift gaming desktop, Maingear joins the ranks of Alienware, Falcon Northwest, and Velocity Micro in providing its customers a distinctive-looking case you can't get anywhere else. And despite a misstep with the build and a questionable processor choice both of which should be easily remedied, we found...
- Product reviews 2009-11-25
- Sony VAIO VGN-NW270F/S
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores.The Sony Vaio VGN-NW270F/S is a stylish, spacious laptop for high-definition fans with low budgets. For a reasonable $699 at Best Buy, the Vaio...
- Product reviews 2009-11-24
- Asus Essentio CG5270-BP004
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores. The Asus Essentio CG5270-BP004 bears a striking resemblance to a young teenager trying too hard. With its oversized, canted case, it's easy to...
- Product reviews 2009-11-24
- Toshiba Satellite U505-S2970
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores.The Toshiba Satellite U505-S2970 is a thin-and-light laptop that is neither thin nor light. It feels solidly built, but this is a 13.3-inch laptop...
- Product reviews 2009-11-24
- HP Pavilion dv6-1375dx
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores. HP had better hope its Pavilion dv6-1375 is not sitting on retail store shelves directly next to the Sony Vaio VGN-NW270F/S. Both are...
- Product reviews 2009-11-24
- HP Pavilion P6230y
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores.The $680 Pavilion P6230y is another midrange HP desktop PC that looks good on paper, but can't keep up with the competition in...
- Product reviews 2009-11-23
- Dell Inspiron i1470-3282CRD
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores.At what cost to battery life? That's the question we're left asking Dell after testing its Inspiron 1470-3282, a $729 laptop sold at Best...
- Product reviews 2009-11-21
- HP Pavilion dv4-1555dx
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores. With its stylish, Imprint-finish chassis, excellent audio output, and remote control, the 14-inch HP Pavilion dv4-1555dx is best suited for students and others...
- Product reviews 2009-11-20
- Gateway One ZX4800-02
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores.The good news about the Gateway One ZX4800-02: it's not a Nettop. Nope, instead this is a full-fledged, $750 all-in-one desktop, complete with a...
- Product reviews 2009-11-20
- Gateway DX4822-01
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores.Although we weren't fans of Gateway's midrange Gateway DX4300-03, the $520 DX4822-01 makes a more convincing argument with budget-minded features like a spacious hard...
- Product reviews 2009-11-20
- Asus Essentio CM5570-AP003
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores.The $480 Asus Essentio CM5570-AP003 is a stripped-down version of the CM5570-AP006 we reviewed in July. It uses the same basic tower but replaces...
- Product reviews 2009-11-20
- Apple iMac (21.5-inch, 3.06Hz Intel Core 2 Duo, Nvidia GeForce 9400M, Fall 2009)
- We awarded Apple an Editors' Choice for its new $1,699 iMac, largely because its 27-inch screen dwarfs its competition in that price range. So what to make of Apple's new lower-end iMac? At $1,199, its 21.5-inch screen is hardly the size leader for its price, and without a touch screen...
- Product reviews 2009-11-17
- Toshiba Satellite E105-S1802
- Editors' note: This review is part of our 2009 Retail Laptop and Desktop Holiday Roundup, which covers specific fixed configurations of popular systems found in retail stores.Toshiba's latest Blue Label laptop from Best Buy, the Satellite E105-S1802, is an exact replica of the company's earlier Satellite E105-S1602 model with one...
- Product reviews 2009-11-16
- Sony Vaio L117FX (Core 2 Quad Q8400s 2.66GHz, 6GB RAM, 1TB HDD, Windows 7 Home Premium)
- Had Apple not introduced a 27-inch iMac for $1,699, we'd have fewer reservations about Sony asking $1,999 for its new 24-inch Vaio L117FX. Yes, HP's TouchSmart 600 expanded on some of Sony's innovations from its previous generation all-in-ones. Sony also doesn't even attempt to match HP's creative multitouch software. But...
- Product reviews 2009-11-13
- HP Pavilion Slimline s5220y
- HP's $480 Pavilion Slimline s5220y is another low-end slim tower PC that offers mediocre performance and equally unexciting performance packaged in a relatively boring case. Its small stature might tempt some of you to use it as a light-duty PC, or even a media-streaming box, but its out-of-date connectivity options...
- Product reviews 2009-11-12
- Dell Studio XPS 8000
- Dell's Studio XPS 8000 offers an attractive chassis and mostly up-to-date features. Its configurations start as low as $699, but our $1,329 review unit is a solid upper-midrange performance desktop that will play games and handle more demanding digital media tasks with little difficulty. For the very price-performance conscious, both...
- Product reviews 2009-11-10
- Dell Inspiron i545s-1476N
- The $480 Inspiron 545s-1476 is the third Dell desktop we've reviewed with the company's current slim tower chassis, and we can't say our opinion has changed since the last time we saw it. We're still satisfied with its design, but we remain disappointed with the features Dell seems to have...
- Product reviews 2009-11-06
- AVADirect Nano Cube
- AVADirect's $2,266 Nano Cube tries to take on Shuttle's XPC H7 5800 at its own small form factor game. Both systems come with smaller-than-normal SFF cases, and each requires sacrifices, even more than with a standard SFF PC, in exchange for its tiny dimensions. Therein lies our problem with this...
- Product reviews 2009-11-04
Premier Vendor Content Whitepapers, webcasts & resources from our Power Center Sponsors
- The best support in the Linux business
-
If Linux is going to power your mission-critical applications, you'd better have the best support known to business. Novell was rated the top provider of Linux technical support.
- Learn more >>
- Save time with automated shipping solutions
-
The Business Essentials Guide provides you useful tools and templates to help grow your business and save you time with automated shipping solutions.
- Visit the UPS Business Essentials Guide
- Microsoft Dynamics CRM Online - Free Six-Month Trial for Eligible Organizations
-
Microsoft Dynamics CRM Online provides fast online access, simple contact management and better sales performance for a low monthly cost - the best value on the market today.
- Learn more about the free, six-month trial offer>>
Popular Sanity Saver Videos
