Memory – Modules

Memory modules are core components used for data storage in computer hardware. They typically refer to memory sticks installed in dedicated slots on the motherboard. They consist of multiple DRAM chips integrated onto a printed circuit board (PCB), enabling high-speed data exchange between the CPU and the memory system. Their primary function is to temporarily store data and instructions during processing, improving system efficiency.

 

1. What are the Components of Memory Modules?

The core structure of a memory module consists of a PCB substrate, soldered DRAM chips, and gold-finger connectors. The PCB typically uses a six-layer design to reduce signal interference, with 8-16 DRAM chips soldered onto the surface to form a memory array. Gold-plated gold-finger connectors provide electrical connections. DIMMs utilize independent pins on both sides to support 64-bit data paths. SOJ (Single-on-J) packaging is the primary packaging format, suitable for high-density assembly.

 

2. What are the Types of Memory Modules?

Based on the pin design and application scenario, memory modules are primarily categorized as follows:

1) DIMM (Dual In-line Module): The mainstream type, such as 168-pin SDRAM and 240-pin DDR5, provides a 64-bit data path and is suitable for desktops and servers.

2) ‌SIMM (Single In-line Module): An early 30- or 72-pin specification with a low upper capacity limit for a single physical bank.

3) ‌Subtype Evolution‌:

UDIMM: An unbuffered design with low latency but less stability.

SO-DIMM: A smaller version used in portable devices such as laptops.

RDIMM/LRDIMM: Registered server-specific modules with improved stability and capacity.

 

3. What are the Working Principles and Key Technologies of Memory Modules?

Memory modules manage data using a physical bank and logical bank architecture. A physical bank is determined by the combined bit width of multiple chips (for example, eight 8-bit chips form a 64-bit data channel), enabling bulk data transfer to the CPU. A logical bank addresses memory cells within the chip using row/column addresses. A single DRAM chip typically integrates four to eight logical banks. Key parameters include:

‌CAS Latency‌: The delay in column address access cycles, which affects response speed.

‌Prefetch Technology‌: For example, DDR5 increases transfer rates to 4800Mbps by extending burst length and using 4-bit prefetch.

 

4. What are the Applications and Development Trends of Memory Modules?

Widely used in PCs, workstations, and servers, compatibility depends on the motherboard slot and chipset limitations (for example, the Intel 430HX chipset requires a single physical bank size of ≤ 64MB). Technological evolutions include:

The transition from SIMM to DIMM, with DDR5 supporting higher bandwidth and energy efficiency.

Innovations include the CXL module, which achieves 32 GT/s transfer speeds via PCIe 5.0 and supports memory pooling technology; the SOCAMM and CAMM2 specifications reduce size and increase capacity to 128GB.