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https://github.com/ucb-bar/riscv-mini

Simple RISC-V 3-stage Pipeline in Chisel
https://github.com/ucb-bar/riscv-mini

chisel riscv rtl

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Simple RISC-V 3-stage Pipeline in Chisel

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# riscv-mini



Author: Donggyu Kim ([email protected])



`riscv-mini` is a simple RISC-V 3-stage pipeline written in Chisel. It has been a crucial example in various project developments,

including [Chisel3](https://github.com/ucb-bar/chisel3.git), [FIRRTL](https://github.com/ucb-bar/firrtl.git),

[Strober](https://bar.eecs.berkeley.edu/projects/strober.html), simulation and verification methodologies.

It implements RV32I of the User-level ISA Version 2.0 and the Machine-level ISA of the Privileged Architecture Version 1.7.

Unlike other simple pipelines, it also contains simple instruction and data caches.



Note that a real-world processor is not the goal of `riscv-mini`.

It is developed as an intermediate example before diving into [rocket-chip](https://github.com/freechipsproject/rocket-chip). 



## Datapath Diagram

![pipeline](diagram.png)



## Getting Started



    $ git clone https://github.com/ucb-bar/riscv-mini.git

    $ cd riscv-mini

    $ make            # generate firrtl & verilog files in generated-src

    

The verilog output file can be used for verilator simulation or the ASIC tool flow.

    

## Running Verilator Simulation



First, generate the verilator binary:



    $ make verilator

    

This will generate `VTile` in the top-level directory.



Now, you can run verilator simulation for a given hex file as follows:



    $ ./VTile  [ 2> ]

    

`` and the pipe to `` are optional. The waveform is dumped to `dump.vcd` and the execution trace is printed in the screen by default.



The following command runs the whole test hex files in verilator and dumps the traces and the waveforms to the 'outputs' directory:



    $ make run-tests



## Unit and Integration Tests with `sbt`



`riscv-mini` provides synthesizable unit & integration tests.

Theres are six sets of unit tests(`ALUTests`, `BrCondTests`, `ImmGenTests`, `CSRTests`, `CacheTests`, `DatapathTests`),

running user-defined test vectors.

To execute them, first launch sbt with `make sbt` and run:



    > testOnly mini.[testname]

  

There are also six sets of integration tests, running the hex files from [riscv-tests](https://github.com/riscv/riscv-tests).

To execute them, also launch `sbt` and run:



    > testOnly mini.[Core|Tile][Simple|ISA|Bmark]Tests

    

`Core` only contains the datapath and the control unit, while `Tile` also contains I$ and D$. `Simple` only runs `rv32ui-p-simple`,

`ISA` runs the whole ISA tests, and `Bmark` runs five benchmarks(`median`, `multiply`, `qsort`, `towers`, `vvadd`). 

Note that all tests in a set run in parallel.



Finally, to run all the tests, just in sbt:



    > test

    

## Running Your Own Program on `riscv-mini`



At this point, you may want to implement and exeucte your custom application on `riscv-mini`. In this case, you need to install RISC-V tools for priv 1.7. This repo provides a script to install the correct version of tools. Run the script as follows:



    $ export RISCV=

    $ ./build-riscv-tools

    

It takes a while to install the toolchain, so please be patient.



This repo also provides a template for your own program in `custom-bmark`. Add your c or assembly code and edit `Makefile`. Next, to compile you program, run `make` in `custom-bmark` to generate the binary, dump, and the hex files. Finally, run the following command in the base directory:



    $ make run-custom-bmark