Different Types of RAM

RAM stems from the fact that data stored in Random Access Memory can be accessed in any random order. RAM memory is very fast both in write and read. There are two different types of RAM, they are:

DRAM (Dynamic RAM):

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Figure: SRAM

▪ It is the most common type of RAM used in computers.
▪ The oldest type is known as Single Data Rate (SDR) DRAM
▪ Newer computers use faster Dual Data Rate (DDR) DRAM.
▪ DDR comes in several versions including DDR2, DDR3, and DDR4, which offer better performance and are more energy-efficient than DDR.
▪ It is not possible to mix DDR2 with DDR3 DRAM in a computer system. Different versions are incompatible

SRAM (Static RAM):

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▪ SRAM is Faster than DRAM
▪ More expensive and bulker, having six transistors in each cell.
▪ For those reasons SRAM is generally only used as a data cache within a CPU itself or as RAM in very high-end server systems.
▪ A small SRAM cache of the most imminently-needed data can result in significant speed improvements in a system

Key Differences Between SRAM and DRAM

1. SRAM is an on-chip memory whose access time is small while DRAM is an off-chip memory which has a large access time. Therefore SRAM is faster than DRAM.
2. DRAM is available in larger storage capacity while SRAM is of smaller size.
3. SRAM is expensive whereas DRAM is cheap.
4. The cache memory is an application of SRAM. In contrast, DRAM is used in the main memory.
5. DRAM is highly dense. As against, SRAM is rarer.
6. The construction of SRAM is complex due to the usage of a large number of transistors. On the contrary, DRAM is simple to design and implement.
7. In SRAM a single block of memory requires six transistors whereas DRAM needs just one transistor for a single block of memory.
8. DRAM is named as dynamic, because it uses a capacitor that produces leakage current due to the dielectric used inside the capacitor to separate the conductive plates is not a perfect insulator hence require power refresh circuitry. On the other hand, there is no issue of charge leakage in the SRAM.
9. Power consumption is higher in DRAM than SRAM. SRAM operates on the principle of changing the direction of current through switches whereas DRAM works on holding the charges.