Have you ever wondered what’s happening behind the scenes when your computer runs a program? It all comes down to memory, specifically RAM (Random-Access Memory). While we often think of it as a place to “store” things, understanding how it works at a hardware level reveals some fascinating secrets about how your computer handles data.

First, let’s get our terms straight. All data in a computer is stored as bits—the fundamental units of information, represented as either a 1 or a 0. These bits are grouped into bytes, with a standard byte containing 8 bits. The physical location where a single bit is stored is called a cell.

DRAM vs. SRAM: The Two Types of RAM

There are two main types of RAM, each with its own advantages and disadvantages. The first, and most common, is Dynamic RAM (DRAM).

Dynamic RAM (DRAM)

DRAM is the primary memory in most computers because it’s cheap and can be packed densely on a chip. A single DRAM cell is simple, consisting of just one capacitor and one transistor. The capacitor stores the electrical charge that represents a bit (1 for charged, 0 for discharged).

The problem? Capacitors are like leaky buckets. They can’t hold a charge forever. To prevent the data from being lost, the memory controller must constantly refresh the state of each cell, reading its charge and then immediately recharging it. This process, known as a memory refresh, is why it’s called “dynamic.”

This constant refreshing uses power, which is why it’s not ideal for devices where power efficiency is a top priority, such as a System on a Chip (SOC) or a microcontroller. This is where the other type of RAM comes into play.

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Static RAM (SRAM)

For applications that need to be fast and low-power, like the memory cache inside your CPU, Static RAM (SRAM) is the go-to solution. A single SRAM cell is much more complex, using six MOSFETs (Metal–Oxide–Semiconductor Field-Effect Transistors) arranged in a flip-flop configuration.

This design makes the cell’s state static—it holds its state as long as power is supplied, with no need for a constant refresh. This saves a significant amount of energy and makes SRAM much faster than DRAM.

However, the complexity of an SRAM cell means it takes up much more space on a chip and is significantly more expensive to manufacture. This is why you see it used for smaller, specialized memory needs rather than the large banks of system memory.

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From RAM to CPU: The Data Journey

Now that we know how data is stored, how does the CPU actually get to it? Let’s follow a piece of data—like the “hello world” string from a program—as it moves from RAM to the processor.

Loading the Data: When a program starts, the necessary data and instructions are loaded from storage (like an SSD or HDD) into RAM.

Addressing Memory: The Memory Management Unit (MMU) organizes this data in RAM by assigning each byte a unique physical address. Think of these addresses as street numbers for every piece of information stored in your computer’s memory.

The CPU’s Request: The CPU’s Control Unit (CU) sends a request for data to the MMU. This request is sent across a parallel bus—a set of wires or “lanes”—that connects the CPU and the memory. For a 64-bit system, the address is sent simultaneously across 64 lanes. Each lane can carry one bit, so a single pulse can transmit an entire 64-bit address.

Retrieving the Data: The MMU receives the address, finds the corresponding data in RAM, and copies it. This data is then sent back to the CPU via a separate bus. It’s crucial to understand that the data isn’t “moved” from RAM; it’s copied from its address to a temporary location within the CPU, such as a register or cache, for processing.

This complex dance of requests and data transfers happens millions of times per second, allowing your computer to run programs, load web pages, and display the graphics you see on your screen. It’s a testament to the incredible engineering that makes our modern computing experience possible.

Hopefully, this sheds some light on the inner workings of your computer’s memory! What other parts of a computer do you find mysterious?