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

3.1 Computers and Their Components

Static RAM (SRAM) vs Dynamic RAM (DRAM)

Think of memory as a library that stores books (data).

SRAM is like a sticky note that stays on the page without needing any extra effort.
DRAM is like a notebook that must be re‑written every few seconds to keep the information fresh.

Both are used in computers, but they differ in how they store bits, how fast they are, and how much space they take.

• Storage cell: SRAM uses flip‑flops (a pair of cross‑coupled NAND gates) to keep a bit. DRAM uses a single capacitor and a transistor.
• Refresh requirement: SRAM never needs refreshing. DRAM must be refreshed every ~10 ms.
• Speed: SRAM is faster (access time < 10 ns). DRAM is slower (access time ~70 ns).
• Density: DRAM can pack many more cells per chip (≈$2^{n}$ cells per bit) because it uses fewer transistors.
• Power consumption: SRAM uses more power when idle because its flip‑flops stay active. DRAM uses less idle power but more during refresh cycles.
• Cost: SRAM is more expensive per bit. DRAM is cheaper and used for main memory.

Key Differences in a Table

Why It Matters

1. Cache memory uses SRAM because it needs to be instantaneous for the CPU.
2. Main memory uses DRAM because it can store more data for less cost.
3. Understanding these differences helps you design better computer systems and troubleshoot performance issues.

🎓 Remember: SRAM = Fast & Sticky, DRAM = Dense & Refresh‑y. Keep this in mind when you think about how a computer remembers information!