Here’s a practical, no-fluff RV32I FPGA implementation roadmap — focused on getting you from zero → running code on hardware.

hase 0 — Setup (1 day)

Goal: Write Verilog, simulate, and compile RISC-V code

• FPGA tools:
  • Vivado (Xilinx)
  • Quartus (Intel)
• Simulation:
  • ModelSim or Verilator
• Toolchain:
  • riscv-gnu-toolchain

👉 Output:

• .c → .elf → .hex working

Phase 1 — Single-Cycle CPU (3–5 days)

Build the minimum working CPU

Modules:

• PC (Program Counter)
• Register File (32 registers)
• ALU (ADD/SUB/AND/OR)
• Instruction Memory (ROM)
• Data Memory (RAM)
• Control Unit

Minimum instructions:

• ADD, SUB
• ADDI
• LW, SW
• BEQ
• JAL

👉 Test goal:

int a = 1 + 2;

If this runs → you have a working CPU.

Phase 2 — Expand RV32I (3–7 days)

Add more instructions

• Logic: XOR, SLL, SRL
• Compare: SLT, SLTU
• Branch: BNE, BLT

Key challenges:

• Immediate decoding (VERY error-prone)
• Branch offset calculation

👉 Goal:

• Run loops and simple if/else

Phase 3 — Pipeline (5–10 days) 🔥

Move from single-cycle → 5-stage pipeline

• IF (Fetch)
• ID (Decode)
• EX (Execute)
• MEM
• WB (Write Back)

Add:

• Pipeline registers (IF/ID, ID/EX…)
• Hazard detection
• Forwarding (bypass)

Hard parts:

• Data hazards
• Control hazards (branches)

👉 Result:

• Multiple instructions running in parallel

Phase 4 — Simulation & Verification (ongoing)

• Write testbenches
• Compare against software results
• Use official tests:
  • RISC-V ISA tests

👉 Goal:

• No silent bugs (this matters more than features)

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🔌 Phase 5 — Run on FPGA (2–3 days)

Hook up real hardware

• Clock
• Reset
• UART (for output)

👉 Example:

printf("Hello RISC-V");

If you see serial output → you made it 🎉

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⚡ Phase 6 — Advanced (optional)

• Cache (I/D cache)
• Branch predictor
• M-extension (mul/div)
• Simple OS / RTOS

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🧠 What You’re Really Doing

You are NOT “writing code”.

You are designing:

• Datapath (how data flows)
• Control logic (what happens when)
• Timing (when it happens)