DRAM (dynamic random-access memory) is the volatile working memory used as main memory in many computers. Each bit is stored as electrical charge in a tiny capacitor controlled by a transistor; because that charge fades, the memory must be refreshed while powered. Turn the power off and the stored contents are lost.
What DRAM is—and how it differs from RAM
RAM, short for random-access memory, is a broad category of working memory that a system can access as needed. DRAM is one kind of RAM, and its high density makes it a common choice for a computer’s main memory. SRAM is another kind of RAM, often used for processor cache. Samsung characterizes SRAM as faster and DRAM as denser, but those are general design trade-offs, not guarantees about every product. Samsung Semiconductor’s DRAM glossary explains the distinction.
| Term | What it means | Typical role |
|---|---|---|
| RAM | A broad category of random-access working memory. | Temporary workspace for a computer or other device. |
| DRAM | Dynamic RAM, whose cells store bits as charge and require periodic refresh. | Main memory in many computers and other devices. |
| SRAM | A different RAM technology; it does not use the DRAM cell design. | Often used for processor cache. |
How a DRAM cell stores a bit
A DRAM cell is built around two components: a capacitor and a transistor. The capacitor holds electrical charge that represents a bit, while the transistor acts as a switch controlling access to that charge. The memory system reads and writes the cells as part of a larger array. Samsung’s explanation of DRAM describes this transistor-and-capacitor structure.
Why DRAM needs refresh
The charge in a capacitor gradually leaks away, even when the computer remains powered. DRAM therefore has to refresh its cells periodically to preserve their data. This upkeep is what “dynamic” refers to in dynamic RAM. Refresh is handled by the memory system; it is not a task users need to perform manually.
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The refresh interval depends on the memory design and operating mode. As one specific example, Micron Technology describes an all-bank refresh for a 16Gb DDR5 SDRAM device in normal refresh mode: refresh occurs once every 3.9 microseconds on average and lasts 295 nanoseconds. Those figures illustrate that device and mode; they are not a universal specification for all DRAM. See Micron’s DDR5 SDRAM: New Features white paper.
Why DRAM is volatile
DRAM only retains its working data while powered and refreshed. When power is removed, the charge is no longer maintained and the contents disappear; DRAM is not persistent storage for files. Samsung Semiconductor states in its DRAM glossary that “DRAM has volatile memory that deletes the saved data once the power is turned off.”
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SDRAM, DDR, and memory speed labels
SDRAM means synchronous DRAM: memory whose operation is synchronized with a system clock. DDR is short for double data rate. DDR memory transfers data on both the rising and falling edges of the clock, enabling two transfers per clock cycle. Modern memory labels such as DDR4 and DDR5 refer to different generations of this memory technology. Micron’s DDR5 overview explains DDR and the terminology used for its rates.
MT/s is transfer rate; MHz is clock frequency
Memory specifications commonly give a transfer rate in MT/s (megatransfers per second). MHz (megahertz) describes clock frequency. They are related but do not mean the same thing: DDR transfers data on two clock edges, so the transfer rate and clock frequency differ. Micron uses MT/s for transfer rate and MHz for clock frequency in its DDR5 terminology. When comparing memory specifications, use the units as stated rather than treating an MT/s number as a clock speed.
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DDR, LPDDR, GDDR, and HBM are not interchangeable
DRAM is a broad family, not one uniform module type. DDR, LPDDR, GDDR, and HBM are families used in different products, including PCs, mobile devices, graphics processors, and accelerators. Their existence does not mean that one kind can be substituted for another: implementation and physical form differ by product and system. Samsung’s DRAM overview describes these families and their application areas.
DIMM is a common term for a memory module: a board or package assembly containing DRAM devices for a system. Desktop, laptop, and server memory can use different module forms and specifications. For instance, Micron’s RDIMM overview covers a registered DIMM type used in server memory contexts. The form factor and memory family must match the device; a label that says DRAM alone is not enough to establish compatibility.
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What to check before upgrading memory
Choose memory for the exact computer or motherboard, not just by capacity or a speed label. Check the manufacturer’s specifications or service documentation for:
- Generation: Confirm the system supports the memory generation you plan to install. DDR4 and DDR5 are not interchangeable: Micron says DDR5 memory and DDR4 motherboards are physically and electrically incompatible (Micron).
- Form factor and module type: Verify whether the device takes desktop, laptop, or server modules and whether it requires a specific type.
- Capacity support: Check the system’s supported capacity, including any per-slot or total limit documented by its manufacturer.
- Transfer rate and timings: Compare the supported MT/s rate and timings in the system specifications; do not assume a higher number will be supported at its rated setting.
There is no universal module choice or compatibility rule that can identify the right upgrade without the computer or motherboard model. Its documentation is the authority for a specific purchase.
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- Enhanced Functionality: Packed with handy features, including a 5x9" precision tracking mouse pad and a built-in phone slot for seamless work or video calls. Plus, enjoy laptop support with the integrated device ledge.
- Cool Comfort: Enjoy a stable surface with our lap desk's dual bolster cushion, designed for comfort and airflow, keeping your lap cool during extended use.
- Durable Surface: Work with confidence on our lap desk's solid surface, featuring a blush pink color, ensuring optimal air circulation to prevent your laptop from overheating.
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