DRAM is an acronym for Dynamic Random Access Memory, the most common form of Random Access Memory (RAM). It has the capacity to store every bit of data in a separate capacitor within a microcircuit.It is a highly volatile memory device because data can be lost when the power supply is removed.
Difference Between DRAM and SRAM
Dynamic RAM (DRAM) is composed of large arrays of very small capacitors. Every capacitor is slowly leaking energy; the information stored will ultimately fade except if the capacitor charge is refreshed from time to time.
DRAMs with an asynchronous interface can react faster to changes in control inputs compared to those with synchronous interface that waits for a clock signal before reacting.
Refreshing DRAM involves reading its contents and instantaneously writing them back. If one or more of the capacitors leaks enough energy and will not be corrected immediately, data corruption will eventually happen.
Due to its refresh requirement, it is termed as a dynamic memory as opposed to Static RAM (SRAM) and other static memory. SRAM has faster capacity yet is much more expensive compared to DRAM. Both DRAM and SRAM, however, are highly volatile RAM so their contents will be lost if the power supply is turned off.
Advantage of DRAM
The main advantage of Dynamic RAM (DRAM) is its structural simplicity. It requires only a capacitor and one transistor per bit, as compared to six transistors used in SRAM (Static RAM). As a result, it can reach a very high density.
Dynamic RAM Packaging
For economic purposes, Dynamic RAMs are generally used on large main memories found in non-handheld game consoles such as Xbox and Playstation, workstations and personal computers.
Other parts of the computer, such as data buffers and cache memories found in hard disks, generally use the Static RAM (SRAM).
Variants of DRAM
The following are some of the common variations of DRAM and their specific descriptions:
1. Asynchronous Dynamic RAM – This variant of Dynamic RAM is the basic form from which all other variants were derived.
An Asynchronous DRAM chip has several number of address inputs (usually 12). It has power connections and only a few number of bidirectional data lines (usually 1 or 4).
2. Synchronous Dynamic RAM (SDRAM) – It is a type of computer memory in solid state, which means that it is based exclusively on the semiconductor, such as bubble memory, chips and transistors.
There is no moving part or mechanical action needed, although a substantial quantity of electromagnetic action occurs within.
3. Double Data Rate (DDR) SDRAM – It is a later improvement of Synchronous Dynamic RAM. It is the type of memory microcircuit commonly used in computers.
It has the capacity to achieve twice the bandwidth (bit rate) compared to its predecessor (Single Data Rate SDRAM) through double pumping, the moving of data on the falling and rising edges of the clock signal without changing the frequency of the clock.
4. Video DRAM (VRAM) – It is a double-ported variant of Dynamic RAM. It is usually utilized to store the frame-buffer in several graphics adapters.
Since it is double-ported, it has two sets of data output pins that can be used simultaneously. The DRAM port, which is the first port, is accessed by the host computer in the same manner done in traditional DRAM. The Video port is the second port, which has the capacity to provide high-speed data channel for the graphics chipset.