Composable Custom Extensions Project

This project aims to enable unlimited, independent, efficient, and robust composition of diverse RISC-V composable extensions, hardware composable extension units (CXUs), and software libraries.

Eventually the work will include specifications, hardware packages, and software libraries. Presently the repo includes only the Draft Proposed RISC-V Composable Custom Extensions Specification (PDF), with hardware CXU core packages, software libraries, tests, and other collateral to come.

It is a work in progress. We request your feedback.

At present this is not a work product of a RISC-V International Working Group, Technical Committee, or subcommittee. Rather we share this work in the hope that it may motivate and inform two hypothetical RISC-V International Task Groups:

1. ISA: CX-ISA TG: Composable Extensions (-Zicx); and
2. non-ISA: CXU-LI TG: Composable Extension Unit Logic Interface.

This work summarizes years of ongoing discussions and prototyping by (alphabetical order): Tim Ansell, Tim Callahan, Jan Gray, Karol Gugala, Olof Kingdren, Maciej Kurc, Guy Lemieux, Charles Papon, Zdenek Prikryl, Tim Vogt.

Build the specification

The spec is built using the RISC-V International asciidoc docker tools image riscvintl/rv-docs.
Linux: install docker. Windows: install a WSL2 Linux distro, plus docker or Docker Desktop.
Run:

cd spec
./docker-make.sh

Copyright (C) 2019-2022, Gray Research LLC [email protected].

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at https://www.apache.org/licenses/LICENSE-2.0.html.

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

The specification subdirectory incorporates design elements from the RISC-V documentation template https://github.com/riscv/docs-dev-guide which uses a Creative Commons Attribution 4.0 International ("CC BY 4.0") license.

RISC-V is a registered trade mark of RISC-V International.