Understanding DDR SDRAM timing parameters
June 25, 2012 // By Deepak Kumar, Sumit Varshney, Sunaina Srivastava and Swapnil Tiwari
Many an engineers who have ever dealt with DDR SDRAM must have been intrigued by the various timing parameters of the DRAM. This article explains the various timing parameters and its impact on the performance of the DRAM.
To begin with, let's first understand how different DDRs are rated or classified. If, we want to buy a DDR module from market, we have to consider many parameters like size, speed, timing specs, brand etc. So, we have many options to choose from. To have a better understanding of these ratings, lets see how these are presented to the buyers. Below is the picture of a DDR SDRAM module.
As seen in figure 1, the module reads DDR3-1600MHz, PC3-12800. So, what does this mean? In DDRx-yyyy, 'x represents the technology generation (example: DDR2, DDR3, DDR) and yyyy represents the DDR clock rate or more appropriately the data rate. DDR (Double Data Rate), as the name suggests, transfers two chunks of data per clock cycle and hence achieve twice the performace as compared to the memory without this feature. It is for this reason that DDR are rated with twice the clock rate at which they function i.e. the data rate.
Usually, DDRx-yyyy convention is followed for the memory chips. But memory chips are not available as such. They are soldered onto tiny PCBs and are termed as memory modules, the speed of which is described as PCx-zzzz. In PCx-zzzz, x represents the same technology generation and zzzz is the maximum bandwidth i.e. maximum transfer rate in MBytes/s.
Maximum Transfer Rate = clock x number of bits / 8
Since memory modules transfer 64 bits at a time, the number of bits will be 64.
Therefore, the formula can be simplified as:
Maximum Theoretical Transfer Rate = clock x 8
Also, one can see the operating voltage and the size of the module mentioned on the memory module. In figure 2, one can easily distinguish between the memory chips and the memory module. The tiny black entities embedded onto the green colour PCB are the memory chips and the complete integrated circuit is the memory module.All news
Freescale mourns employees on missing Malaysian flight
March 10, 2014
Nearly three days after Malaysia Airlines Flight MH370 vanished from radar screens and as the mystery remains about what ...
Arrow Electronics signs EMEA distribution for Variscite
Apple design wins lift Bosch to top of MEMS ranking
Smartphone app oximeter meets hospital standards
Haptic lens converts light into touch
The MEMS market - who are the winners, the losers
March 10, 2014
How dynamic the market for MEMS is shows a recent survey from IHS technology. These microelectromechanical systems are increasingly ...
Optical sensor improves spot welding process
SmartMesh IP wireless sensor network starter kit
Conspiracy alleged over Rousset wafer fab closure
- DSM presents: Select the best plastic for DDR4
- Wireless Sensor Network Challenges and Solutions
- Putting FPGAs to Work in Software Radio Systems Handbook
- Real-Time Spectrum Analysis for Troubleshooting 802.11n/ac WLAN Devices
InterviewWi-Fi is ‘open’ for business, which is good news for mobile subscribers
Following the news that Netgear has built a Facebook-linked amenity Wi-Fi option into its routers, enabling businesses to offer free Wi-Fi in return for liking the company Facebook page, David Nowicki, ...
Filter WizardCheck out the Filter Wizard Series of articles by Filter Guru Kendall Castor-Perry which provide invaluable practical Analog Design guidelines.
Linear video channel
READER OFFERRead more
This month, Freescale is giving away ten RIoTboards, worth 74 dollars each, for EETimes Europe's readers to win.
Designed to run Android operating systems efficiently or to run under Linux, the board is based on the Freescale i.MX 6Solo processor; using the ARM Cortex-A9 architecture.
And the winner is...
In our previous reader offer, Crystal Display was giving...Read more
December 15, 2011 | Texas instruments | 222901974
Unique Ser/Des technology supports encrypted video and audio content with full duplex bi-directional control channel over a single wire interface.