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Nr.1 reason is that you need a open ISA in order to have an open processor. Therefore you can only have proper OpenHardware movement with an open processor. Th

by nickik 6y ago

Nr.1 reason is that you need a open ISA in order to have an open processor. Therefore you can only have proper OpenHardware movement with an open processor. The RISC-V foundation was only created in 2015 before that it was basically a research project so saying anything RISC-V related is 'always' 5 years away is a strange statement. And I also don't know where you get 'good enough', RISC-V is not a processor, its and ISA and we know that ISA have relatively little impact implementation speeds. We already have RISC-V processors at the same node as ARM processors that beat them in many criteria.

astrange 6y ago
> we know that ISA have relatively little impact implementation speeds But this is not true, decoders cannot make up for everything. ISAs can also do a lot to improve software security, not to mention ease of use. RISC-V is just not well designed. Though it might be good enough… https://gist.github.com/erincandescent/8a10eeeea1918ee4f9d9982f7618ef68 https://gist.github.com/erincandescent/8a10eeeea1918ee4f9d99...
- nickik 6y ago
  Performance is not one thing, we have processors from so small they can almost not be seen to gigantic AI chips. RISC-V made some design choices and some people like some of them and some people don't like others, just like with anything else in the world. Christopher Celio as part of his PhD did ISA comparison and found no way that RISC-V is systematically worse, in fact in many situations its better. David A Patterson, Dave Ditzel and many other long time engineers in this space seem to really like it. And btw, you could make a much longer The Good, The Bad, The Ugly list about ARM as well. By that definition no ISA is well designed.
- brucehoult 6y ago
  That's the opinion of one ARM engineer I've never heard of. Here's the opinion of probably THE most important ARM engineer of the 1990s and 2000s, Dave Jaggar who developed the ARM7TDMI, Thumb, Thumb2. https://www.youtube.com/watch?v=_6sh097Dk5k https://www.youtube.com/watch?v=_6sh097Dk5k Check at 51:30 where he says "Are there any ARM snipers? No ... I would Google RISC-V and find out all about it. They've done a fine instruction set, a fine job [...] it's the state of the art now for 32-bit general purpose instruction sets. And it's got the 16-bit compressed stuff. So, yeah, learning about that, you're learning from the best."
  - astrange 6y ago
    Did he also design AArch64? Because I've noticed it can be used to design very fast processors, yet abandons most decisions in ARM7 and Thumb. I was just curious about how SIMD worked in RISC-V so I looked it up… and apparently RISC-V doesn't have SIMD, instead it brings back microcoded large vector operations from the 70s, and the RISC-V designers called SIMD bad and compared it to the opioid crisis because it means there are too many instruction opcodes? https://www.sigarch.org/simd-instructions-considered-harmful/ https://www.sigarch.org/simd-instructions-considered-harmful... So I'm now even less impressed and also slightly offended. This is not realistic, short vectors are important and easy to do in hardware.
    - nickik 6y ago
      Many codes can be expressed much better with Vectors and there is also much ability to further extend it in the future. You can do short vectors with the RISC-V Vector extension and you can implement them in a simply way as well. Have you worked with both or did you just form your opinion based on what you are used to? Again, RISC-V is not one thing, its modular. The 'V' extension is considered to be the right thing for most serious processors. However there is also the 'P' extension, for embedded that does Packed SIMD.

by nickik 6y ago

astrange 6y ago

> we know that ISA have relatively little impact implementation speeds But this is not true, decoders cannot make up for everything. ISAs can also do a lot to improve software security, not to mention ease of use. RISC-V is just not well designed. Though it might be good enough… https://gist.github.com/erincandescent/8a10eeeea1918ee4f9d9982f7618ef68 https://gist.github.com/erincandescent/8a10eeeea1918ee4f9d99...

nickik 6y ago
Performance is not one thing, we have processors from so small they can almost not be seen to gigantic AI chips. RISC-V made some design choices and some people like some of them and some people don't like others, just like with anything else in the world. Christopher Celio as part of his PhD did ISA comparison and found no way that RISC-V is systematically worse, in fact in many situations its better. David A Patterson, Dave Ditzel and many other long time engineers in this space seem to really like it. And btw, you could make a much longer The Good, The Bad, The Ugly list about ARM as well. By that definition no ISA is well designed.
brucehoult 6y ago
That's the opinion of one ARM engineer I've never heard of. Here's the opinion of probably THE most important ARM engineer of the 1990s and 2000s, Dave Jaggar who developed the ARM7TDMI, Thumb, Thumb2. https://www.youtube.com/watch?v=_6sh097Dk5k https://www.youtube.com/watch?v=_6sh097Dk5k Check at 51:30 where he says "Are there any ARM snipers? No ... I would Google RISC-V and find out all about it. They've done a fine instruction set, a fine job [...] it's the state of the art now for 32-bit general purpose instruction sets. And it's got the 16-bit compressed stuff. So, yeah, learning about that, you're learning from the best."
- astrange 6y ago
  Did he also design AArch64? Because I've noticed it can be used to design very fast processors, yet abandons most decisions in ARM7 and Thumb. I was just curious about how SIMD worked in RISC-V so I looked it up… and apparently RISC-V doesn't have SIMD, instead it brings back microcoded large vector operations from the 70s, and the RISC-V designers called SIMD bad and compared it to the opioid crisis because it means there are too many instruction opcodes? https://www.sigarch.org/simd-instructions-considered-harmful/ https://www.sigarch.org/simd-instructions-considered-harmful... So I'm now even less impressed and also slightly offended. This is not realistic, short vectors are important and easy to do in hardware.
  - nickik 6y ago
    Many codes can be expressed much better with Vectors and there is also much ability to further extend it in the future. You can do short vectors with the RISC-V Vector extension and you can implement them in a simply way as well. Have you worked with both or did you just form your opinion based on what you are used to? Again, RISC-V is not one thing, its modular. The 'V' extension is considered to be the right thing for most serious processors. However there is also the 'P' extension, for embedded that does Packed SIMD.