5 ms·

>To be among the first to use an open source, RISC-V CPU in a regular computer? A portable one, no less?! To be a pioneer of a more open hardware future? That s

by bragr 5y ago

>To be among the first to use an open source, RISC-V CPU in a regular computer? A portable one, no less?! To be a pioneer of a more open hardware future? That sounds like an absolute privilege. Is this an actual open source processor? I can't find any info on it either way. A lot of the conversation around RISC-V seems to conflate the open source nature of the ISA with the the actual implementation. Even the reference implementations are BSD licensed so people are allowed to distribute proprietary derivatives to say nothing of completely proprietary implementations. If all or most of the implementations are propriety, I feel like it is a mostly lateral move from ARM as, although it is not open source, the ARM ISA is readily available [1], and the same kinds of rarified CPU engineering and academic circles that will have influence in the RISC-V Foundation, already influence ARM. [1] https://developer.arm.com/architectures/cpu-architecture/a-profile/exploration-tools https://developer.arm.com/architectures/cpu-architecture/a-p...

snvzz 5y ago
>Is this an actual open source processor? AIUI the SoC is not open, but the CPU design it contains, XuanTie C906, is. It would even be decent if it had standard V extension, but sadly it uses an incompatible pre-standard draft.
- phkahler 5y ago
  Is there really any software yet that uses the V?
  - sitkack 5y ago
    All software will use V once it is available. Any operation done in a loop over fixed size elements can have V applied to it. It is much more powerful than SIMD.
    - owlbite 5y ago
      I must admit, I've yet to find a performance relevant loop that I can't do in simd that doesn't also have dependencies on previous iterations such that no magic instruction set is going to help unless it's capable of time travel.
      - namibj 5y ago
        LLVM's Polly[0] can often do magic there, by renumbering[1] the iteration space. Where variable vector length instructions help is decoupling the chunk size from the machine code, because they take care of the remainder that doesn't fit in whole vectors/chunks in an agnostic fashion. It's so you can get at least most of the gains from wider vector units without needing to change the code. [0]: https://polly.llvm.org/ https://polly.llvm.org/ [1]: https://en.wikipedia.org/wiki/Polytope_model https://en.wikipedia.org/wiki/Polytope_model
      - Dylan16807 5y ago
        It's not that you couldn't have used fixed SIMD, it's so it can rescale the SIMD automatically.
        owlbite 5y ago
        Right, but portable code != portable performance. See also: OpenCL. There's also the observation "keep simd vectors small but many" (e.g. Apple's arm chips) over "super long vectors" (intel avx512) is superior as it is much more flexible whilst delivering similar performance for tasks that are amenable to larger vectors. Having an architecture pushing towards the latter seems a retrograde step to me.
    - limoce 5y ago
      Any software that uses memcpy will use V once glibc is updated.
- avianes 5y ago
  XuanTie C906 is not open-source. They just open-source a light version of the C906, the OpenC906. For instance OpenC906 does not contain the vector extension. But even the OpenC906 is only partially open-source. They only disclosed verilog code generated by an internal tool, so the real design source code is not open. Worse, they don't open source testbenchs which makes any modification or verification very tedious.
mnd999 5y ago
The BSD license is definitely open source. It’s just not ‘free software’ in the FSF sense.
- snvzz 5y ago
  BSD license absolutely is "free software" in the FSF sense. The four freedoms are guaranteed by it, and it is even listed explicitly in their list of free software licenses.
  - Nursie 5y ago
    > The four freedoms are guaranteed by it Nope. The BSD license does not guarantee source to users. It's very free in that it places minimal restrictions what can be done with, but it doesn't guarantee the four freedoms to people who (for instance) receive binaries of modified works. I'm not saying it's bad because of this, I don't want to start a flame war here.
    - deleted 5y ago
      [deleted]
    - snvzz 5y ago
      GNU+FSF[0], OSI[1] and me disagree with you. But you can have your own opinion, sure. [0]: https://www.gnu.org/licenses/license-list.html https://www.gnu.org/licenses/license-list.html [1]: https://opensource.org/licenses https://opensource.org/licenses
      - Nursie 5y ago
        It's hardly just my opinion, there's a lot of opinion out there on the web that agrees with me. It's very hard to see how this definition on the OSI site - "Where some form of a product is not distributed with source code, there must be a well-publicized means of obtaining the source code for no more than a reasonable reproduction cost, preferably downloading via the Internet without charge" Fits licenses like BSD/MIT license which do not require source access to be provided. And the FSF say this - "To decide whether a specific software license qualifies as a free software license, we judge it based on these criteria to determine whether it fits their spirit as well as the precise words" So they give themselves pretty loose rules for inclusion there. I would say that the BSD license, with its very few restrictions, is definitely open source and its spirit is all about freedom. But I really don't see that it supports the four freedoms, specifically freedom 2 (from the FSF site here: https://www.gnu.org/philosophy/free-sw.html https://www.gnu.org/philosophy/free-sw.html) - "The freedom to study how the program works, and change it so it does your computing as you wish (freedom 1). Access to the source code is a precondition for this."

by bragr 5y ago

snvzz 5y ago

>Is this an actual open source processor? AIUI the SoC is not open, but the CPU design it contains, XuanTie C906, is. It would even be decent if it had standard V extension, but sadly it uses an incompatible pre-standard draft.

phkahler 5y ago
Is there really any software yet that uses the V?
- sitkack 5y ago
  All software will use V once it is available. Any operation done in a loop over fixed size elements can have V applied to it. It is much more powerful than SIMD.
  - owlbite 5y ago
    I must admit, I've yet to find a performance relevant loop that I can't do in simd that doesn't also have dependencies on previous iterations such that no magic instruction set is going to help unless it's capable of time travel.
    - namibj 5y ago
      LLVM's Polly[0] can often do magic there, by renumbering[1] the iteration space. Where variable vector length instructions help is decoupling the chunk size from the machine code, because they take care of the remainder that doesn't fit in whole vectors/chunks in an agnostic fashion. It's so you can get at least most of the gains from wider vector units without needing to change the code. [0]: https://polly.llvm.org/ https://polly.llvm.org/ [1]: https://en.wikipedia.org/wiki/Polytope_model https://en.wikipedia.org/wiki/Polytope_model
    - Dylan16807 5y ago
      It's not that you couldn't have used fixed SIMD, it's so it can rescale the SIMD automatically.
      - owlbite 5y ago
        Right, but portable code != portable performance. See also: OpenCL. There's also the observation "keep simd vectors small but many" (e.g. Apple's arm chips) over "super long vectors" (intel avx512) is superior as it is much more flexible whilst delivering similar performance for tasks that are amenable to larger vectors. Having an architecture pushing towards the latter seems a retrograde step to me.
  - limoce 5y ago
    Any software that uses memcpy will use V once glibc is updated.
avianes 5y ago
XuanTie C906 is not open-source. They just open-source a light version of the C906, the OpenC906. For instance OpenC906 does not contain the vector extension. But even the OpenC906 is only partially open-source. They only disclosed verilog code generated by an internal tool, so the real design source code is not open. Worse, they don't open source testbenchs which makes any modification or verification very tedious.

mnd999 5y ago

The BSD license is definitely open source. It’s just not ‘free software’ in the FSF sense.

snvzz 5y ago
BSD license absolutely is "free software" in the FSF sense. The four freedoms are guaranteed by it, and it is even listed explicitly in their list of free software licenses.
- Nursie 5y ago
  > The four freedoms are guaranteed by it Nope. The BSD license does not guarantee source to users. It's very free in that it places minimal restrictions what can be done with, but it doesn't guarantee the four freedoms to people who (for instance) receive binaries of modified works. I'm not saying it's bad because of this, I don't want to start a flame war here.
  - deleted 5y ago
    [deleted]
  - snvzz 5y ago
    GNU+FSF[0], OSI[1] and me disagree with you. But you can have your own opinion, sure. [0]: https://www.gnu.org/licenses/license-list.html https://www.gnu.org/licenses/license-list.html [1]: https://opensource.org/licenses https://opensource.org/licenses
    - Nursie 5y ago
      It's hardly just my opinion, there's a lot of opinion out there on the web that agrees with me. It's very hard to see how this definition on the OSI site - "Where some form of a product is not distributed with source code, there must be a well-publicized means of obtaining the source code for no more than a reasonable reproduction cost, preferably downloading via the Internet without charge" Fits licenses like BSD/MIT license which do not require source access to be provided. And the FSF say this - "To decide whether a specific software license qualifies as a free software license, we judge it based on these criteria to determine whether it fits their spirit as well as the precise words" So they give themselves pretty loose rules for inclusion there. I would say that the BSD license, with its very few restrictions, is definitely open source and its spirit is all about freedom. But I really don't see that it supports the four freedoms, specifically freedom 2 (from the FSF site here: https://www.gnu.org/philosophy/free-sw.html https://www.gnu.org/philosophy/free-sw.html) - "The freedom to study how the program works, and change it so it does your computing as you wish (freedom 1). Access to the source code is a precondition for this."