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> the current "compiled" spec document is about 5 years behind the actual production ISA How could I verify this information?
by shiftingleft 4y ago
> the current "compiled" spec document is about 5 years behind the actual production ISA
How could I verify this information?
- therealcamino 4y agoThat was my question, too. What instructions have been undocumented for five years? What non-standardized extensions exist in SiFive cores?
- pclmulqdq 4y agoRead the RISC-V foundation website. There are numerous "ratified" parts of the RISC-V instruction set that are not in the latest "compiled" spec document.
- therealcamino 4y agoSaying a "compiled" spec is out of date may be technically accurate (or not, I don't have any idea) but if open, published documentation of the ratified extensions is on the web site, it's misleading to cite it as evidence that the spec is not open. And I know that the draft specifications are open for public comment prior to being ratified, so it's not a secret what's under development, either.
- pclmulqdq 4y agoI never said that it wasn't actually open source. I just said that the openness hasn't actually created meaningful competition, because there is a single company in control of the specs that abuses that control to create a moat. For a concrete example, the bitmanip extensions (which provide significant increases in MIPS/MHz) were used by SiFive in commercial cores before ratification and finalization. No other company could do that because SiFive employees could just change the spec if they did. They're doing the same thing with vector/SIMD instructions now to support their machine learning ambitions.
- nradov 4y agoIt's kind of hilarious how complex some "reduced" instruction sets have become.