What Is SRAM?
SRAM (Static RAM) is a very fast RAM type that needs no refresh to hold data. It's the memory of places that need speed.
How Does It Work?
Each bit is stored in a latch (flip-flop) circuit made of a few transistors. As long as power is applied the data stays fixed; that's why it's called "static".
Difference From DRAM
DRAM holds data in a capacitor and must be refreshed constantly; SRAM needs no refresh and is much faster. But an SRAM cell takes more space and is expensive.
| Property | SRAM | DRAM |
|---|---|---|
| Speed | Very high | Medium |
| Refresh | Not needed | Needed |
| Cost/density | Expensive, low | Cheap, dense |
Why Still Volatile?
Although SRAM needs no refresh it's still volatile: data is erased when power is cut. "Static" means the data preserves itself while power is present, not persistence.
Where Is It Used?
Processor cache, microcontrollers' internal working memory, high-speed buffers and network-device memory.
Why Expensive and Low-Density?
SRAM needs about six transistors per bit; this means far fewer bits in the same area than DRAM. The high transistor count both raises the cost and lowers the density, so SRAM is used only in small regions where speed is critical.
Common Mistakes
- Assuming it's persistent: SRAM also loses its contents when power is cut.
- Choosing it for main memory: being expensive, gigabytes of SRAM aren't economical.
- Battery backup: some systems use battery-backed SRAM to preserve its data.
Frequently Asked Questions
Why is SRAM so fast?+
Is cache memory SRAM?+
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