Explain the differences between Static RAM (SRAM) and Dynamic RAM (DRAM)

Resources | Subject Notes | Computer Science

3.1 Computers and their components: Static RAM (SRAM) vs. Dynamic RAM (DRAM)

Introduction

Random Access Memory (RAM) is a crucial component of any computer system. It's used to store data that the processor is actively using. There are two main types of RAM: Static RAM (SRAM) and Dynamic RAM (DRAM). This section will explore the fundamental differences between these two types, focusing on their operation, speed, cost, and applications.

Static RAM (SRAM)

SRAM stores each bit of data using a circuit made of flip-flops. A flip-flop is a stable circuit that holds a 1 or a 0 as long as power is supplied. Because it uses flip-flops, SRAM does not need to be refreshed.

Key characteristics of SRAM:

  • Operation: Uses flip-flops to store data.
  • Speed: Very fast. SRAM is significantly faster than DRAM.
  • Cost: More expensive per bit than DRAM.
  • Size: Larger individual memory cells compared to DRAM.
  • Power Consumption: Higher power consumption compared to DRAM.
  • Complexity: More complex to manufacture.

Dynamic RAM (DRAM)

DRAM stores each bit of data as an electrical charge within a capacitor. Capacitors leak charge over time, so the data stored in DRAM needs to be periodically refreshed to maintain its integrity. This refreshing process is what gives DRAM its name.

Key characteristics of DRAM:

  • Operation: Uses capacitors to store data. Requires periodic refreshing.
  • Speed: Slower than SRAM.
  • Cost: Less expensive per bit than SRAM.
  • Size: Smaller individual memory cells compared to SRAM.
  • Power Consumption: Lower power consumption compared to SRAM.
  • Complexity: Less complex to manufacture.

Comparison Table

Feature SRAM DRAM
Storage Mechanism Flip-flops Capacitors
Speed Fast Slower
Cost per bit Expensive Inexpensive
Cell Size Large Small
Refresh Requirement No Yes
Power Consumption High Low
Complexity Complex Simple

Summary

In summary, SRAM offers superior speed but at a higher cost and power consumption. DRAM provides a more cost-effective solution for large memory capacities, accepting a trade-off in speed. The choice between SRAM and DRAM depends on the specific requirements of the application. SRAM is typically used for cache memory in processors, where speed is paramount. DRAM is used for main system memory, where capacity is more important.

Suggested diagram: A diagram showing a simplified representation of SRAM and DRAM cells. SRAM cell showing flip-flops, DRAM cell showing a capacitor and a transistor.