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I wonder to what extent the digital logic design is open source. The RISC-V core ought to be, but what about the memory controller or PCIE root complex, (or USB
by etaioinshrdlu 6y ago
I wonder to what extent the digital logic design is open source. The RISC-V core ought to be, but what about the memory controller or PCIE root complex, (or USB3)? Those parts are also very important.
- gchadwick 6y agoJust because it's RISC-V doesn't mean it's open source. RISC-V is an open architecture so anyone can make an implementation but those implementations can be closed source. SiFive have released some open source stuff (https://github.com/sifive/freedom https://github.com/sifive/freedom) but the majority of their work is closed source IP. In a way they're quite similar to arm.
- userbinator 6y agoJust like ARM, the only thing standard is the core and there is massive (and almost always publicly undocumented) diversity of everything else.
- brandmeyer 6y agoNot just like ARM. You don't need a license to implement a RISC-V compatible machine. IIUC, you only need to pass a compliance test to brand your machine RISC-V and use the trademark.
- Taniwha 6y agoThere's not just one RISC-V core, one of the great things is that there are many, of varying complexity and performance. Some are very open source some are not. There's already GCC and clang support, linux is here too.
- gnufx 6y agoGCC doesn't have support for this system's vector unit in the development source as far as I can see. Does LLVM?
- jim-gcc 6y agoThe vector extension is still in draft and still changing. We don't want to add support that we will have to remove later if the proposal changes again. But we have support in the rvv-intrinsic branch at github.com/riscv/riscv-gnu-toolchain. There is also LLVM work, they have different rules for development, so are handling this differently.
- gnufx 6y agoThanks. That's rather what I'd expect, but I was surprised at hardware being announced with (some version of) the vector extension and wondered what support there would be for it. Is it reasonable to ask what you might expect in terms of changes if you started playing with an initial implementation, or is it still wide open? (Assuming the right Jim!)
- jim-gcc 6y agoThe vector extension is getting close to being formally submitted, so things should settle down. There was a major compatibility break a few weeks ago, but I'm hoping that was the last one. We won't know for sure until it is approved. Vendors advertising vector support will have to maintain their own toolchains if they implement drafts. Most vector support is in IP cores, and they can be changed to follow the draft. There is no problem until someone makes an ASIC. Unfortunately Alibaba already did that and they are going to have lots of problems as they are incompatible with everyone else. But most everyone else is waiting for the official vector extension before making ASICs.