6 ms·
What is the "2-read-1-write register access constraint" mentioned in the introduction?
by pw98745bnt 5y ago
What is the "2-read-1-write register access constraint" mentioned in the introduction?
- bem94 5y agoIt means that each instruction reads no more than two general purpose registers (i.e. inputs), and writes at most one. When you build CPUs, register files are expensive components, and the more parallel accesses to them you need, the more expensive they become. RISC architectures generally rely on only reading two operands and writing only one result. Sometimes this rule is broken, but RISC-V tries to stick to it unless there's an extremely good reason.