Difference Between SRAM and DRAM

The main difference between SRAM and DRAM is that the SRAM does not require refresh cycles to hold the data while the DRAM requires periodical refresh cycles to retain data.

The CPU requires more time to access the hard disk. Therefore, the executing processes are placed in the main memory or the RAM. RAM allows accessing data faster than storage medium such as hard disk drives, solid state drives. It stands for Random Access Memory. The capacity of the RAM defines how fast the device performs. It is a volatile memory and requires a continuous flow of current to maintain the data in the RAM. Therefore, powering off the current will erase the content in RAM. There are two types of RAM called SRAM (Static RAM) and DRAM (Dynamic RAM). The difference between them lies in the refresh cycle requirement.

Key Areas Covered

1. What is SRAM
     – Definition, Functionality
2. What is DRAM
     – Definition, Functionality
3. Difference Between SRAM and DRAM
     – Comparison of Key Differences

Key Terms

SRAM, DRAM, Operating System

What is SRAM

SRAM stands for Static RAM. It is a semiconductor memory and uses flip flops to store each bit or data. It does not require periodical refresh cycles to retain data. Therefore, it does not use any complex hardware circuit. The main advantage of SRAM is that it is fast. Cache is a fast memory that holds the frequently used data by the CPU. SRAM is used for cache. As SRAM is faster than DRAM, it has a minimum access time to data.

Figure 1: SRAM Cell

SRAM is used for personal computers routers, peripheral devices, CPU cache, register files, etc. It is also used in industrial and scientific subsystems and automotive electronics that requires a high performance. Overall, SRAM is fast and reliable, but it is more expensive.

What is DRAM

DRAM stands for Dynamic Random Access Memory. It is a semiconductor memory that stores each bit in a separate capacitor with an integrated circuit. The capacitor can be charged or discharged and represents the logical one and logical zero. There is some leakage current, and the capacitor will lose charge. It can erase the data on the chip. To avoid this issue, DRAM needs to use a refresh circuit. This circuit constantly rewrites the data in the capacitor and restores them to their original charge. Therefore, DRAM memory is dynamic and requires continuous refresh cycles to retain data.

Figure 2: DRMA

Overall, DRAM is not as fast as SRAM, but it is faster than other storage components such as hard disk. It is the most common type of main memory, and it is not as expensive as SRAM. It is frequently used for digital electronics applications that require low cost and high capacity of memory.

Difference Between SRAM and DRAM

Definition

SRAM is a type of semiconductor memory that uses bi-stable latching circuitry (flip flop) to store each bit. DRAM is a type of random access semiconductor memory that stores each bit of data in a separate tiny capacitor within an integrated circuit.

Stands for

The SRAM stands for Static Random Access Memory. DRAM stands for Dynamic Random Access Memory.

Speed

SRAM is very fast. DRAM is faster than secondary storage such as hard disk, but it is not as fast as SRAM.

Refresh Cycles

Further, SRAM does not require refresh cycles to retain data. DRAM requires periodical refresh cycles to retain data.

Hardware Complexity

As DRAM requires refreshing, it has more complex circuitry and timing requirements compared to SRAM.

Usage

SRAM is used for CPU cache while DRAM is used for the computer’s main memory. DRAM is the most common main memory type.

Access time

Also, SRAM require minimum time to access data. DRAM requires more time to access data than SRAM.

Power consumption

SRAM consumes less power than DRAM in lower frequencies. It becomes comparable in higher frequencies.

Memory Cell Structure

The structure of SRAM is complex. It has flip flops. On the other hand, the structure of DRAM is simple. It has a transistor and a capacitor.

Density

Density refers to the number of memory cells per unit area. SRAM has a lower density comparing to DRAM.

Cost

SRAM is expensive than DRAM.

Conclusion

RAM is a volatile memory in a computer system. There are two types of RAM called SRAM and DRAM. The difference between SRAM and DRAM is that the SRAM does not require refresh cycles to hold the data while the DRAM requires periodical refresh cycles to retain data.

Reference:

1. “Static Random-Access Memory.” Wikipedia, Wikimedia Foundation, 10 July 2018, Available here.
2. “Dynamic Random-Access Memory.” Wikipedia, Wikimedia Foundation, 16 July 2018, Available here.

Image Courtesy:

1. “SRAM Cell (6 Transistors)” By Inductiveload – Own work (Public Domain) via Commons Wikimedia
2. “DRAM DDR2 512” By Appaloosa 11:45, 10 August 2006 (UTC) – taken by Appaloosa (CC BY-SA 3.0) via Commons Wikimedia