Lab 7: Becoming a Processor Designer

“Procezzor”

By now, you should be quite comfortable with CMake, SystemVerilog, C++, and general team operations and expectations.

The Time Has Come

Now, you must choose what you wish to work on for the semester. Your choices are outlined below.

Core

The heart of an SoC is the CPU Core. As part of the core team, you will work on the design and implementation of a CPU core capable of executing the RISC-V-32I instruction set.

Many of the individual modules that make up the core have been outlined in detail for easier implementation so you can get started writing Verilog code right away. You can find our getting started guide here. We also have interfaces between modules that need to be built. More information can be found here.

For those with more advanced skills and seeking a deeper level of involvement on the core design itself, many of the modules that make up the core have yet to be fully outlined for implementation and we encourage you to take a shot at making those outlines yourself, a list of where exactly each module stands can be found here.

Finally, for those with the requisite knowledge, skills, and passion, much of the overall core design still needs to be finalized. This includes things like the caches, branch prediction, hazard detection, and more. Designing these components and functions will require a strong background in computer architecture as you’ll need to be ready to validate and troubleshoot both, your designs and the designs of others. You can see the block diagram of the current core design on the repository, and you can find the functionality and design documentation for the more complex components here.

Memory

An SoC needs memory. As part of the memory team, you will work on the memory simulator and integrating it with the bus. You will work closely with the AMBA team whilst designing and implementing the memory manager since the memory manager is a subordinate on the AMBA high-performance bus.

Our SoC’s memory is an experiment in using OpenRAM, an open-source RAM compiler. As part of the team, you will be expected to become an expert in OpenRAM and how it interacts with our chip.

As it stands, we have RAM and ROM generation scripts, but they need to be thoroughly tested and deciphered. If you wish to work on memory, reach out to leadership since the team is currently defunct.

AMBA

AMBA is the interconnect architecture which connects various parts of the SoC together. It is the vertebrae of the chip, connecting core to important subordinates like RAM and ROM, GPIO, UART, etc, and to each other, when needed.

An intriguing facet of working on AMBA is comprehending and translating ARM’s specification. Trivial concepts have been summarised for easy access but you will still be expected to read the spec sheets, propose and discuss component designs with the team.

Additionally, our implementation is one of very few open-source AMBA implementations on the internet, which allows us a unique challenge of not having a reference. Everything you produce will be one of its kind and all of us will learn and grow from that process.

But perhaps, AMBA’s most interesting challenge includes translating logic into RTL. Everything AMBA does is easy to think about programmatically, but it is admittedly quite challenging to translate into SystemVerilog. Every day, the team learns novelties in SystemVerilog and our extended toolchain.

If working on AMBA speaks to you, read more about it here.

Onboarding/Documentation

A project of this magnitude needs thorough technical documentation for the sake of future team members and strangers who wish to see our work. Documentation includes writing module and interface templates, development guides, improving onboarding labs and the team’s website, and other written issues that don’t directly involve coding/Verilog.

It is strongly recommended that you join a development team such as Core, Memory or AMBA as well as working on documentation. You can be responsible for that team’s docs while also contributing to component development.

Something Else Entirely

You can work on things that our team has never worked on before, such as, the simulator, or develop software for the chip to be. Alternatively, you could be individualist and prefer not to work in a team - feel free to work on one of the many peripherals we need.

Whatever the case may be, if none of the above speaks to you, reach out to leadership to discuss next steps so we can equip you for success.

Overwhelmed by Choice

Don’t worry if you’re not quite sure what you’d like to work on. You can work on as many teams as you wish to. Just don’t spread yourself too thin.

Take the week to explore how various teams operate, talk to the Czars, and other team members.

After Deciding

Once you know what team(s) you wish to work on, inform the project manager, and check in with your Czar.

Happy processor designing!