🧠 SRAM vs DRAM: Core Differences
| Feature | SRAM (Static RAM) | DRAM (Dynamic RAM) |
|---|---|---|
| 🧬 Cell Design | Uses 6 transistors per bit | Uses 1 transistor + 1 capacitor per bit |
| 🔁 Refreshing | No need to refresh as long as powered | Needs constant refreshing (thousands of times per second) |
| ⚡ Speed | Faster | Slower |
| 🧠 Density | Lower (larger cells = less data per chip) | Higher (smaller cells = more data per chip) |
| 🔌 Power Consumption | Lower idle power, but higher dynamic power | Higher power due to constant refreshing |
| 💸 Cost | Expensive | Cheaper |
| 🔧 Complexity | More complex to design | Simpler to design and manufacture |
| 📍 Usage | CPU cache (L1, L2, L3) | Main system memory (RAM modules) |
🔧 Real-World Use:
| Component | Likely Type |
|---|---|
| CPU Cache | SRAM |
| Laptop/Desktop RAM (DDR4/DDR5) | DRAM |
| GPU onboard cache | SRAM |
| Smartphone system RAM | DRAM (LPDDR) |
🧬 Why These Differences Exist
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SRAM cells hold data as long as power is on by keeping the transistors in a stable flip-flop configuration.
-
DRAM cells use a capacitor to store data, which leaks charge over time—so it must be refreshed regularly (~every 64ms).
⚙️ Technical Summary:
| Spec | SRAM | DRAM |
|---|---|---|
| Access Time | ~1–2 ns | ~50–100 ns |
| Transistors per Bit | 6 | 1 + 1 capacitor |
| Integration Level | Low | High |
| Volatility | Volatile | Volatile |
🧠 Interview-Ready Explanation:
SRAM (Static RAM) is fast, expensive, and doesn’t need refreshing, making it ideal for small, high-speed memory like CPU caches. DRAM (Dynamic RAM) is slower and requires constant refreshing, but it’s cheaper and denser, making it suitable for main memory. The choice between them is a trade-off between speed, size, and cost.