Definition: dynamic RAM

The common type of computer memory and generally available in the form of DDR SDRAM (double data rate synchronous dynamic RAM) chips. LPDDR (low-power DDR) was designed for mobile devices but is commonly used in AI servers to save electricity. All types of dynamic RAM, including high-speed HBM, use a similar cell structure. See high bandwidth memory.

Dynamic RAM uses one transistor and one storage capacitor for each bit. It is denser, less costly and slower than "static RAM," which is temporary storage next to the CPU known as "cache memory" ("cash memory"). See cache.

AI Demand Changed the Game
Due to the enormous demand for memory in AI data centers, the price of regular dynamic RAM rose dramatically in 2026. For example, DDR5 modules that cost $100 in 2025 were advertised at $400 a year later. See SDRAM.

RAM Is a Total Loser
Unlike flash memory chips in SSDs that hold their content when the power is turned off, memory requires constant power. The capacitors in memory are electrical storage tanks that do a terrible job of holding a charge. The capacitors are refreshed several times each second, which is why everything in memory is lost when the power is turned off. See flash memory.

A Lot of Bits Today
In 1968, dynamic RAM was patented by IBM, and the first chips came from Intel and Mostek in the early 1970s with a capacity of 1,000 bits. Today, 16 gigabytes of dynamic RAM is entry level for PCs, and gaming PCs can have 256GB. An AI server rack can have many terabytes of HBM and LPDDR RAM. See static RAM and memory types.

A Dynamic RAM Cell

DRAM cells are very simple. The combination of voltage on the row and column lines charges a capacitor. The only problem is that the capacitors keep losing their charges, and the bits must be read and re-written to the same state several times each second.