The RISC-V Foundation publish the official specification.
- Online viewer: https://riscv.org/specifications/
- GitHub source: https://github.com/riscv/riscv-isa-manual
These are un-official conversions to HTML from the GitHub source (There is an effort to do it officially here):
ABI References from the RISC-V GitHub:
- Standard ABI: https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md
- Embedded EABI: https://github.com/riscv/riscv-eabi-spec/blob/master/EABI.adoc
Machine Readable Resources:
- RISC-V official opcodes is available on RISC-V GitHub: https://github.com/riscv/riscv-opcodes
- YAML ISA data used for this blog: https://github.com/five-embeddev/riscv-isa-data
Other Resources:
- A “green card” summary of the ISA: RISCVGreenCardv8-20151013.pdf