Overview

A 6-stage core, 2-Wide Superscalar, implementing the RiscV ISA (RV32IM). Features:

• Dual Fetch & Dual Issue
• Dynamic Branch Prediction
• Register Renaming Scheme
• OoO Execution
• Non-blocking data cache

Directory Hierarchy

The folder hierarchy is organised as follows:

• images: schematics
• rtl : contains all the synthesisable RTL files
• sva : contains related x-checks and assertions for the design
• rig_tb : contains the Random Instruction Generator and associated TB environment
• sim : contains scripts for running in Questasim

Repo State

Current State & Limitations

• Support for "RV32I" Base Integer Instruction Set
• Support for “M” Standard Extension for Integer Multiplication and Division
• Verification status: Unit verification & Top level verification has taken place
• Partially implemented: Decode for additional instructions that are not yet supported (System, floating point, CSR) and exception detection
• The svas present have only been using in simulation and not in any formal verification process

Future Optimisations

• Replace MUL/DIV units with optimised hardware, to reduce execution latency and decompress a lot of the paths

Future Work

• Floating Point & Fixed point arithmetic
• CSR, SYSTEM instructions and Priviledged ISA
• Exception detection and Interrupt handling
• Virtual Memory
• 64bit support
• Align to future versions of the RISC-V ISA. Current document version supported is 20191213 of the Unpriviledged ISA manual

How to Compile

The /sim directory is used for the simulation flow and it contains detailed instructions for both the flow and compiling C code. That way you can generate your own executable file and convert it to a memory file suitable for the CPU. Examples (code and precompiled files) are included in the /sim/examples directory.

To compile:

• include a compiled memory.txt file inside the /sim directory
• run the compile.do in questa with: "do compile.do"

The testbench hierarchy can be seen below:

TB Level Hierarchy: ->tb -> module_top -> Processor_Top

Hierarchy Name	Details
tb	top level of the TB, instantiating the datapath
module_top	The top level of the cpu datapath, connecting the memories and the surrounding logic with the core
processor_top	The top level of the core datapath

Run the RIG TB

A second testbench environment is provided inside /rig_tb, featuring a Random Instruction Generator (RIG). For more information on how to setup, configure and run the testbench consult the README inside its directory.

License

This project is licensed under the MIT License.