What Is DRAM?
DRAM (Dynamic RAM) is a dense and economical RAM type that holds each bit in a small capacitor. It's the main memory of computers.
How Does It Work?
Each bit consists of a capacitor and a transistor. Whether the capacitor is charged/empty carries the 1/0 information. This simple cell allows memory of very high density (many bits, little space).
The Need for Refresh
A capacitor loses its charge over time; so DRAM's contents must be refreshed thousands of times per second. This constant refresh makes it slower and slightly more power-hungry than SRAM.
| Property | DRAM | SRAM |
|---|---|---|
| Cell | 1 capacitor + 1 transistor | Multiple transistors |
| Density | High | Low |
| Refresh | Needed | Not needed |
Why Main Memory?
Being cheap and dense, gigabytes of capacity can be produced economically. So the main RAM of computers and phones is DRAM (DDR derivatives).
Where Is It Used?
Computer and server main memory (DDR), phone RAM, game consoles and graphics-card memory (GDDR).
Access Latency
DRAM uses row-column addressing; to reach a datum, first the row is opened then the column is selected. These steps add extra latency compared to SRAM. Modern DDR memories largely hide this latency by transferring sequential data very fast (high bandwidth).
Common Mistakes
- Assuming it's persistent: DRAM is volatile; it's erased when power is cut.
- Speed expectation: where cache speed is wanted, DRAM alone isn't enough.
- Skipping refresh: refresh management is essential in the design.
Frequently Asked Questions
What is DDR?+
Why is DRAM cheap?+
Search parts related to "What Is DRAM?"
Find the right part by comparing price, stock and distributors.