1. The Role of Memory

Memory (RAM, Random Access Memory) is one of the core components of a computer. Its main functions include:

• Storing data: When the CPU processes data, it retrieves it from the hard drive (SSD/HDD) and temporarily stores it in memory for faster access.
• Improving computing speed: Compared to storage drives, memory has much faster read/write speeds, reducing CPU wait times.
• Temporary data storage: Memory is volatile, meaning data is lost when power is turned off, making it unsuitable for long-term storage.

Simple analogy:

• The hard drive is like a bookshelf, storing a large number of books (data), but retrieving a book (reading data) is slow.
• Memory is like a desk, where frequently used books are placed for quick access.
• The CPU is like a reader who prefers to grab books from the desk (memory) rather than repeatedly fetching them from the bookshelf (hard drive).

2. Structure of Memory

A memory module consists of several key components:

(1) Storage Chips (DRAM)

• DRAM (Dynamic Random Access Memory) is the core of PC memory.
• Made up of capacitors + transistors, where each storage unit holds 1 bit of data (0 or 1).
• Since capacitors leak charge, they require constant refreshing, which is why it’s called dynamic RAM.

(2) Memory Controller

• Modern CPUs integrate a memory controller that manages data read and write operations.

(3) SPD (Serial Presence Detect) Chip

• A small ROM chip that stores memory specifications (frequency, timing, voltage, etc.).
• The BIOS/UEFI reads SPD data to configure memory settings automatically.

(4) PCB (Printed Circuit Board)

• Connects storage chips, power circuitry, and data transmission pathways.

(5) Gold Fingers (Connectors)

• Connects the memory module to the motherboard’s RAM slot, enabling data transfer.

(6) Heat Spreader (Present in High-Performance RAM)

• Some high-performance memory modules come with metal heat spreaders or thermal pads to dissipate heat.

3. How Memory Works

1. CPU Accesses Memory
   • When the CPU needs data, it first checks the L1/L2/L3 cache (which is much faster but has limited capacity).
   • If the cache does not contain the data, the CPU sends a request to memory.
2. Memory Controller Reads Data
   • The process involves the following steps:
     1. RAS (Row Address Strobe): Selects the row where the target data is stored.
     2. CAS (Column Address Strobe): Selects the column containing the target data.
     3. The memory controller decodes the address and retrieves the data.
3. Data is Returned to the CPU
   • The retrieved data is stored in the cache for faster access in future operations.
4. Refreshing (Refresh Cycle)
   • Since DRAM relies on capacitors, which lose charge over time, it requires periodic refreshing to maintain data integrity.

4. Major Types of Memory

Memory can be classified based on different criteria. Let’s analyze them in detail:

(1) Classification by Technology

Modern PC memory primarily uses DDR (Double Data Rate Synchronous DRAM).

(2) Classification by DDR Generation

Reason for Classification:

Each DDR generation improves bandwidth, reduces latency, and lowers power consumption, meeting increasing performance demands.

(3) Classification by Form Factor

(4) Classification by Purpose

(5) Classification by Channel Configuration

5. Conclusion

• Memory is a high-speed buffer for the CPU, storing temporary data to ensure system smoothness.
• Modern PCs primarily use DDR4 and DDR5 memory, with DDR5 offering higher bandwidth and lower power consumption.
• Memory performance depends on frequency, timing, and channel configuration. Dual-channel or higher improves overall speed.
• High-end users may opt for overclocking memory (XMP/EXPO), while servers require ECC memory for stability.