The Fusion-Core ISA has two main points: making your common case fast, and compatible with every other version of an implementation. By defining a main core instruction set, co-processors can be added to extend the ISA, though to be supported, they will need to be registered. More information on the ISA can be found in the documentation which resides in the github repository: https://github.com/bit0fun/Fusion-Core/tree/master/doc . Any questions or interest in contributing to the project will be answered at this email: dylan@fusion-core.org