What is DRAM?

The goal of any memory device is to quickly store and retrieve data in the memory array.

DRAM, or Dynamic Random-Access Memory, is the medium that is used for the temporary storage of information by today's personal computers and mainframes.

Each DRAM component is comprised of numerous cells, or storage locations, made up of a capacitor and a transistor which can either hold an active or an inactive state. Each DRAM cell is referred to as a Bit (binary digit) and is commonly used to reference the smallest amount of information that a computer can work with. A DRAM's cell is said to hold a value of '1', an active state, when it holds a charge beyond a certain level. It is said to have '0', an inactive state, when the charge is below a certain level. Because of the nature of a capacitor, it is necessary to recharge, or refresh, the state in which the cell exists, as over time, the capacitor loses its charge (The loss of charge results in the loss of information).

DRAM cells are combined into a large array that is used to store vast amounts of information translated binarily by computers. The DRAM elements are arranged in specific groups organized in terms of Rows and Columns, with each cell having a specific Row/Column reference (Address location).

Each cell can be accessed (read from/written to) by specifying the exact address at which it is located. A Byte is defined as a group of eight of these DRAM cells. Today's machines use large amounts of these cells assembled in memory modules containing Megabytes per module (106 bytes).

DDR SDRAM DDR2 SDRAM DDR3 SDRAM
System Clock (MHz) 100/133/166/200 100/133/166/200 100/133/166/200
Speed (in MHz) 200/266/333/400 400/533/667/800 800/1066/1333/2000
JEDEC Description PC-2000/PC-2100
PC-2700/PC-3200
PC2-3200/PC2-4200
PC2-5300/PC2/6400
PC3-6400/PC3-8500
PC3-10600/PC3-12800
Voltage 2.5V 1.8V 1.5V
CAS Latency 2,2.5,3 3,4,5 5,6,7,8,9,01
ODT (On Die Termination) Not Supported Supported Supported
Component Package TSOP FBGA   FBGA 
Thermal Sensor No No   Optional