DRAM is the volatile working memory that holds data and instructions a computer is using right now. Each cell stores a bit as electrical charge in a capacitor, controlled by a transistor; because that charge gradually leaks away, the memory must be refreshed while the computer is powered. Turn the power off and the contents are lost.
What DRAM is—and how a cell stores data
DRAM stands for dynamic random-access memory. A cell is built from a tiny capacitor and a transistor: the capacitor’s electrical charge represents a bit, and the transistor controls access to that charge. A computer combines very large numbers of these cells to hold working data.
The charge does not remain perfectly stable. DRAM therefore refreshes its cells periodically to preserve their contents. As an example—not a universal timing rule—Micron describes an all-bank refresh for a 16Gb DDR5 SDRAM device in normal refresh mode that occurs once every 3.9 microseconds on average and lasts 295 nanoseconds. Micron’s DDR5 refresh explanation gives the device and operating-mode context.
Is DRAM the same as RAM?
No. RAM is the broad category of random-access working memory; DRAM is one type of RAM and is widely used as a computer’s main memory. SRAM is another type. Samsung characterizes SRAM as faster and commonly used for processor cache, while DRAM’s higher density makes it suitable for main memory. Those are common design roles, not guarantees about every product. Samsung Semiconductor’s DRAM glossary explains the cell structure and distinction.
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DRAM is volatile: it holds data while powered, not as a permanent place to keep files. Samsung puts it plainly: “DRAM has volatile memory that deletes the saved data once the power is turned off.” Save files you need to keep to persistent storage, such as an SSD or hard drive.
What DDR, LPDDR, GDDR and HBM mean
These names describe different DRAM families designed for different products and system requirements. They are not interchangeable module formats.
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| Family | Common context | What to know |
|---|---|---|
| DDR | PC and server main memory | DDR means double data rate: data transfers on both rising and falling edges of the clock. DDR generations such as DDR4 and DDR5 are not interchangeable on a system. |
| LPDDR | Mobile devices and other power-conscious designs | A low-power DRAM family; its system implementation is not simply a desktop DIMM. |
| GDDR | Graphics processors | A DRAM family used for graphics memory, with implementations distinct from ordinary system-memory modules. |
| HBM | Accelerators and other high-bandwidth systems | A high-bandwidth memory family used in specialized designs, not a plug-in replacement for a standard desktop module. |
Samsung’s DRAM overview describes these families and their product contexts. The exact implementation and compatibility depend on the device.
How to read DDR speed labels: MT/s versus MHz
MT/s means millions of transfers per second, a measure of data-transfer rate. MHz measures clock frequency. Because DDR transfers data on both clock edges, the transfer rate and clock frequency are not the same number; don’t treat an MT/s rating as an MHz clock reading. Micron explains the distinction on its DDR5 DRAM page.
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A memory module has to match the system that will use it. Before buying a replacement or upgrade, check the computer or motherboard manufacturer’s specifications rather than relying on a product label alone.
- Generation: confirm the supported DDR generation. DDR5 memory and DDR4 motherboards are physically and electrically incompatible, according to Micron.
- Form factor and module type: desktop, laptop and server memory assemblies differ. Server configurations may use registered DIMMs (RDIMMs); consult the exact system documentation. See Micron’s RDIMM overview.
- Capacity and rate: verify the system’s supported capacity and transfer rate, stated in MT/s. Check supported timings as well when selecting between compatible options.
There is no universal module that fits every computer. Use the device or motherboard specification to confirm compatibility before ordering.
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