mips-cpu - A MIPS CPU written in Verilog

An implementation of a MIPS CPU written in Verilog. This project is in very early stages and currently only implements the most basic functionality of a MIPS CPU.

• 32-bit MIPS processor

• implemented in Verilog

• 5 stage pipeline

• static branch not taken branch predictor

• branch detection in decode (stage 2)

• supports stalls to avoid read after write (RAW) and other hazards

• can forward from memory (stage 4) and write back (stage 5) to avoid stalls

Much of the design was inspired by the book "Computer Organization and Design" by David A. Patterson and John L. Hennessy (4th ed. 2008).

This project also includes a full set of test benches. These are invaluable as a quick check to verify that new changes have not disrupted previously working functionality.

This project requires a Verilog simulator, such as Icarus, the Gcc compiler, and a Gcc MIPS cross compiler. To check if your system has the required programs installed run the check-install.sh script.

$ ./check-install.sh
Checking for required programs...
  mips-linux-gnu-objcopy
  mips-linux-gnu-as
  iverilog
Please install the missing programs and retry.

The tests are located in the verilog/test/ directory. Everything is built and run using the make command.

make

There are two parts to each test: the Verilog code, and the assembly code. The Verilog code uses a generic CPU test bench (cpu_tb.v) from which a specific test is built using a specific assembled .hex file. The .hex file is produced by assembling the .asm file using the Gcc MIPS cross compiler and converting it to ASCII hex suitable for use with Verilog. Then the Verilog code, using a simulator such as Icarus Verilog, can be run to execute the assembly instructions and produce a dump of its output (.out). Finally, the output file (.out) can be diffed against a known good output file (.check) to see if there are any differences.

For more information about these steps refer the Makefile in verilog/test/.

Jeremiah Mahler [email protected]
http://github.com/jmahler

Copyright © 2015, Jeremiah Mahler. All Rights Reserved.
This project is free software and released under the GNU General Public License.