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
ADCs for high dynamic range – successive-approximation or sigma-delta?
September 01, 2014
Maithil Pachchigar, an applications engineer with Analog Devices Inc., looks at trade-offs that must be considered when choosing ...
Microchip in Pursuit of CSR
Samsung Funds III-V FinFETs in US Lab
A question of Europe
Trinamic's stepper motor package gets you started
Winged parcel delivery: Google's way
August 29, 2014
While there is still debate about if legislation would ever allow swarms of commercial drones to fly over our heads, Google ...
Two-inch Super AMOLED display fits Samsung smartwatch plans
UK armed forces consider lithium sulfur batteries
Small cell market to hit $4.8 billion in five years
- Power Modules: The New Super Power
- Flexible Performance for Network Security Appliances
- Digital Power Management Reduces Energy Costs While Improving System Performance
- Using RF Recording Techniques to Resolve Interference Problems
InterviewA question of Europe
Sir Peter Bonfield sits on the board and has advisory roles in many international companies and universities. With more than 45 years of experience in electronics, computers and communications, here he ...
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, Trinamic Motion Control is offering you to win one of four TMCM-1043 development kits for its highly integrated, NEMA 17-compatible TMCM-1043 stepDancer stepper motor module.
Offering designers an easy-to-use PC-based GUI that allows one-click modification of motor drive current, micro-stepping and other key parameters, the intuitive kits are custom designed and developed for...MORE INFO AND LAST MONTH' WINNERS...
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.