3.1 Computers and their components - SRAM vs DRAM

Random Access Memory (RAM) is a type of computer memory that can be accessed in any order. There are two main types of RAM: Static RAM (SRAM) and Dynamic RAM (DRAM). They differ significantly in their structure, speed, cost, and usage. This section will detail these differences.

Static RAM (SRAM)

SRAM uses flip-flops to store each bit of data. A flip-flop is a circuit that holds a bit as long as power is supplied. Because it uses flip-flops, SRAM does not require periodic refreshing.

Key Characteristics of SRAM:

• 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 than DRAM.
• Complexity: More complex circuitry.

Dynamic RAM (DRAM)

DRAM stores each bit of data as an electrical charge within a capacitor. Capacitors leak charge over time, so DRAM requires periodic refreshing to maintain the data. This refreshing process involves reading the data and rewriting it back into the capacitor.

Key Characteristics of DRAM:

• Speed: Slower than SRAM.
• Cost: Less expensive per bit than SRAM.
• Size: Smaller individual memory cells compared to SRAM.
• Power Consumption: Lower power consumption than SRAM.
• Complexity: Simpler circuitry.

Comparison Table

Feature	SRAM	DRAM
Storage Cell	Flip-Flops	Capacitors and Transistors
Speed	Fast	Slower
Cost per bit	Expensive	Inexpensive
Size	Larger	Smaller
Refresh Requirement	No	Yes
Power Consumption	High	Low
Complexity	Complex	Simple

Summary:

SRAM is used in applications where speed is critical, such as CPU caches. DRAM is used for main system memory because its lower cost and higher density make it more suitable for storing large amounts of data.

Diagram