🚀 RV32I Tutorial #1: What is RV32I? The Real Starting Point of a CPU

Most people think CPUs understand code.
They don’t.

A CPU only understands instructions.

And if you want to understand how a CPU really works, you need to start from the simplest possible instruction set:

👉 RV32I

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🧠 1. What is RV32I?

RV32I is the base integer instruction set of the RISC-V architecture.

• RV → RISC-V
• 32 → 32-bit architecture
• I → Integer instructions

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👉 In simple terms:

RV32I defines the minimum set of instructions needed to build a working CPU.

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🔍 2. Why RV32I Matters

Modern CPUs are complex.

But they are all built on simple foundations.

RV32I gives you that foundation.

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Instead of hundreds of instructions, RV32I has:

👉 ~40–50 instructions

That’s it.

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And with just these instructions, you can:

• perform arithmetic
• load and store data
• make decisions (branching)

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👉 Which means:

You can build a real CPU with RV32I alone

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⚙️ 3. What Kind of Instructions Does RV32I Include?

RV32I instructions fall into a few key categories:

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🟢 Arithmetic

• ADD, SUB
• ADDI

👉 Used for basic math

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🔵 Logical

• AND, OR, XOR

👉 Used for bit operations

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🟡 Memory Access

• LW (Load Word)
• SW (Store Word)

👉 Move data between memory and registers

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🔴 Control Flow

• BEQ, BNE
• JAL, JALR

👉 Change the execution path

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👉 Everything a program does can be expressed using these.

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🔄 4. From Code to Instructions

Let’s look at a simple example:

int a = 1 + 2;

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This does not run directly on the CPU.

It gets compiled into instructions like:

ADDI x1, x0, 1
ADDI x2, x0, 2
ADD  x3, x1, x2

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👉 The CPU executes these one by one.

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🧩 5. What the CPU Actually Does

At runtime, the CPU is not “running code”.

It is doing this:

Read data → Compute → Write result

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For example:

ADD x3, x1, x2

The CPU:

1. Reads x1
2. Reads x2
3. Adds them
4. Writes result to x3

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👉 That’s all.

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🧠 6. Key Insight

Most people think:

Programming = writing logic

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But at the CPU level:

Programming = moving data + simple operations

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👉 RV32I exposes this reality.

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⚡ 7. Why This Is the Starting Point

If you understand RV32I:

• You understand what a CPU can actually do
• You understand how software becomes hardware operations
• You can start building your own CPU

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👉 Without this layer, everything above is just abstraction.

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🚀 8. What’s Next?

Now that you understand RV32I,

the next question is:

👉 Where does the data live?

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👉 Next Tutorial:

RV32I Tutorial #2: What is a Register File?

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📌 Summary

• RV32I is the minimal RISC-V instruction set
• It defines what a CPU can do
• It contains ~40–50 instructions
• All programs reduce to these instructions

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👉 One sentence:

RV32I is where software becomes something a machine can execute