- ISA separated into small base ISA and support for extensions
- JAL stores the address of the instruction following the jump (pc+4) into register rd. Calling convention is x1 as return address and x5 as alternate link register. Return address stack can be manipulated by JAL/JALR.
- Aligned loads and stores are guaranteed to execute atomically, misaligned loads and stores are not
- Each hart observes its own memory operations as if they are executed in sequential program order. RISC-V observes a relaxed memory model between harts. Explicit FENCE instructions are required to guarantee ordering between memory operations from different harts.
- FENCE is used to order I/O and memory accesses as viewed by other RISC-V harts, external devices, and co-processors. No other hart or external device can observe any operation in the successor set following a FENCE operation before any operation in the predecessor set before the FENCE.