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RISC-V is only an instruction set architecture, not a microarchitecture. It describes how things work from a software point of view, but it does not require any
by mrob 7y ago
RISC-V is only an instruction set architecture, not a microarchitecture. It describes how things work from a software point of view, but it does not require any specific implementation, and it does not require anything to be fast. You can implement instructions with microcode or software if you want to.
- childintime 7y ago> You can implement instructions with microcode or software if you want to. Note that I'm specifically not talking about microcode, nor emulation in software. So I gather the answer is "no", and the instructions not directly implemented must be implemented in microcode instead of trapping them to a library.
- garmaine 7y agoNo, your original assumption is correct. It is explicitly stated (though I can't remember where) that it is acceptable for a compliant RISC-V core to trap and emulate instructions that it doesn't natively support.