# Resources and Specifications

This page aims to collect all the resources and specifications we need in one place for quick access. We will try our best to keep links here up-to-date. Feel free to add more links here.

# RISC-V Instruction Set Architecture

The Libre RISC-V Project is building a hybrid CPU/GPU SoC. As the name of the project implies, we will be following the RISC-V ISA due to it being open-source and also because of the huge software and hardware ecosystem building around it. There are other open-source ISAs but none of them have the same momentum and energy behind it as RISC-V.

To fully take advantage of the RISC-V ecosystem, it is important to be compliant with the RISC-V standards. Doing so will allow us to to reuse most software as-is and avoid major forks.

* Official compiled PDFs of RISC-V ISA Manual: <https://github.com/riscv/riscv-isa-manual/releases/latest>
* Working draft of the proposed RISC-V Bitmanipulation extension: <https://github.com/riscv/riscv-bitmanip/blob/master/bitmanip-draft.pdf>
* RISC-V "V" Vector Extension: <https://riscv.github.io/documents/riscv-v-spec/>

Note: As far as I know, we aren't using the RISC-V V Extension directly at the moment. But, I am putting it here for informative comparison purposes to our own vector extension called SV.

# IEEE Standard for Floating-Point Arithmetic (IEEE 754)

Almost all modern computers follow the IEEE Floating-Point Standard. Of course, we will follow it as well for interoperability.

* IEEE 754-2019: <https://standards.ieee.org/standard/754-2019.html>

Note: Even though this is such an important standard used by everyone, it is unfortunately not freely available and requires a payment to access. However, each of the Libre RISC-V members already have access to the document.

# Khronos Standards

The Khronos Group creates open standards for authoring and acceleration of graphics, media, and computation. It is a requirement for our hybrid CPU/GPU to be compliant with these standards, especially Vulkan and OpenCL being the most important. SPIR-V is also important for the Kazan driver.

* SPIR-V 1.5 Specification Revision 1: <https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html>
* SPIR-V OpenCL Extended Instruction Set: <https://www.khronos.org/registry/spir-v/specs/unified1/OpenCL.ExtendedInstructionSet.100.html>
* SPIR-V GLSL Extended Instruction Set: <https://www.khronos.org/registry/spir-v/specs/unified1/GLSL.std.450.html>
* Vulkan 1.1.122: <https://www.khronos.org/registry/vulkan/specs/1.1-extensions/html/index.html>
* OpenCL 2.2 API Specification: <https://www.khronos.org/registry/OpenCL/specs/2.2/html/OpenCL_API.html>
* OpenCL 2.2 Extension Specification: <https://www.khronos.org/registry/OpenCL/specs/2.2/html/OpenCL_Ext.html>
* OpenCL 2.2 SPIR-V Environment Specification: <https://www.khronos.org/registry/OpenCL/specs/2.2/html/OpenCL_Env.html>

Note: I'm not sure what the plan is for OpenGL. Are we doing that in hardware or using Zink to run OpenGL on top of Vulkan?