DRAMmodules

DRAM modules are printed circuit boards that provide volatile memory for computers by mounting DRAM memory chips on a single substrate. The most common form factors are DIMMs for desktops and servers, and smaller SO-DIMMs for laptops and compact systems. There are variants designed for reliability and scalability, including ECC (error-correcting) modules, registered (buffered) modules, and load-reduced memory (LRDIMMs) used in servers.

On the module, DRAM chips are organized into banks, rows, and columns. Data is transferred over a data bus that is typically 64 bits wide for standard non-ECC DIMMs; ECC modules add an extra 8 bits for error checking. The memory controller uses SPD (Serial Presence Detect) to read the module’s timing, voltage, and size information. DRAM must be refreshed periodically to retain data, which memory controllers manage automatically.

Technology generations for DRAM modules are standardized under JEDEC and include DDR, DDR2, DDR3, DDR4, and DDR5. Each generation improves bandwidth and reduces operating voltage. Typical consumer DDR4 DIMMs operate around 1.2 volts with data rates from roughly 1600 to 3200 MT/s, while DDR5 offers higher speeds and efficiency and supports larger capacities. Server-class DIMMs may be registered or load-reduced to improve stability and scalability in multi-channel configurations.

Capacities vary widely. Desktop modules commonly range up to 32 GB per DIMM for DDR4 and up to 64 GB for DDR5 in consumer systems, with server modules capable of higher per-DIMM capacities depending on technology and platform. The memory topology, including rank configuration and timings, influences latency and bandwidth, and module choice is guided by system requirements for performance, power, and reliability.