DRAMchips

Dynamic random-access memory chips, or DRAM chips, are a type of volatile memory used for primary storage in computers and other digital devices. Each bit is stored as an electrical charge in a tiny capacitor within a memory cell, and a single transistor acts as a switch to access the cell. Because capacitors leak charge, DRAM requires regular refreshing to preserve stored data.

DRAM cells are arranged in a two-dimensional array of rows and columns. A decoder selects a row via word lines, while sense amplifiers and bit lines read or write data for the selected column. A typical DRAM cell uses one transistor and one capacitor, which makes DRAM relatively dense and inexpensive compared with other memory technologies.

Refresh and timing: To retain information, the charge in each capacitor must be periodically refreshed. Refresh operations read and then restore charge for a subset or all rows, controlled by memory controllers. Refresh consumes power and can affect latency, leading to the use of optimized scheduling in modern memory systems.

Variants and evolution: SDRAM (synchronous DRAM) aligns with system clocks. Successive generations—DDR, DDR2, DDR3, DDR4, and DDR5—increase data rate and efficiency. Specialized DRAM types include GDDR for graphics, LPDDR for mobile, and high-bandwidth memory (HBM) used in GPUs and accelerators. DRAM is typically implemented as single chips that form DIMMs or used in high-density stacked configurations.

Manufacture and use: The chips are produced by major manufacturers such as Samsung, SK hynix, and Micron, on deep sub-micron fabrication processes. They are packaged as standalone dies or integrated into modules, arranged in memory arrays within computers, servers, and consumer electronics. Reliability features include error-correcting codes (ECC) in servers and strategies to mitigate issues such as density-related failure modes and row hammer.