A completely open ISA that is freely available to
academia and industry.
A real ISA suitable for direct native hardware
implementation, not just simulation or binary
An ISA that avoids "over-architecting" for a particular
microarchitecture style (e.g., microcoded, in-order,
decoupled, out-of-order) or implementation technology (e.g.,
full-custom, ASIC, FPGA), but which allows efficient
implementation in any of these.
An ISA separated into a small base integer ISA,
usable by itself as a base for customized accelerators or
for educational purposes, and optional standard extensions,
to support general-purpose software development.
Support for the revised 2008 IEEE-754 floating-point
An ISA supporting extensive user-level ISA extensions and
32-bit, 64-bit, and 128-bit address space variants for
applications, operating system kernels, and hardware
An ISA with support for highly-parallel multicore or
manycore implementations, including heterogeneous
Optional variable-length instructions to both
expand available instruction encoding space and to support
an optional dense instruction encoding for improved
performance, static code size, and energy efficiency.
A fully virtualizable ISA to ease hypervisor
An ISA that simplifies experiments with new
supervisor-level and hypervisor-level ISA designs.
Right now, you can download the final
user-level ISA specification,
draft compressed ISA specification,
draft privileged ISA specification, and
RISC-V software tools including a
GNU/GCC software tool chain,
GNU/GDB debugger, an
LLVM compiler, an
QEMU, and a
A high-performance, energy-efficient Rocket processor (a 64-bit
RISC-V single-issue in-order core), suitable for both
high-speed simulation and full synthesis, is available for
download. The Sodor
repository of educational RISC-V cores, written in Chisel is also available.
The cores include a microcoded processor, an unpipelined
processor, and 2, 3, and 5-stage pipelines.
repository contains infrastructure for implementing Rocket
cores on Zynq FPGAs, like the Zybo and ZedBoard.
To sample the architecture without installing anything,
try out ANGEL, a
on a simulated RISC-V machine in your browser.
Our intent is to provide a long-lived open ISA with
significant infrastructure support, including documentation,
compiler tool chains, operating system ports, reference
software simulators, cycle-accurate FPGA emulators,
high-performance FPGA computers, efficient ASIC
implementations of various target platform designs,
configurable processor generators, architecture test suites,
and teaching materials. Initial versions of all of these have
been developed or are under active development. This material
is to be made available under open-source licenses.