5 ms·

I wonder if NASA has a clue that RISC-V's ISA is open-source but SiFive's designs certainly aren't.

deleted 4y ago
[deleted]
Jtsummers 4y ago
You can't launch an ISA into space and expect it to do anything. At some point, hardware has to be designed and built based on that ISA.
- babypuncher 4y ago
  Nonsense; I printed out a copy of the AGC instruction set reference, stuffed it in one of my model rockets, and it turned into a Saturn V mid-flight.
- UltraViolence 4y ago
  Then what advantage does it have over ARM or x64? The ISA being open doesn't seem to make any difference at all.
  - brucehoult 4y ago
    RISC-V is massively simpler (and smaller silicon and lower energy use) for the same performance. Oh, and significantly smaller code size too, so everything from ROMs to RAM (if code is loaded to RAM) to icache can be sized smaller. The ISA being open source means that if SiFive goes out of business or changes its product lineup, or starts to make buggy stuff, or charge too much ... no matter what happens, the customer is free to find another vendor to make software-compatible chips. As we've found out with ARM this week, even if one company with ARM's highest and most expensive form of license, the Architecture License Agreement (ALA), makes a CPU design they are not allowed to transfer or sell that design to another company that also has an ALA without ARM's explicit permission. Or so ARM claims. Let's see what the courts decide about that.
    - awill 4y ago
      >>RISC-V is massively simpler (and smaller silicon and lower energy use) for the same performance. Per my understanding RISC-V has nothing even close performance-wise to Arm's high-end stuff. So isn't it apples to oranges?
      - justahuman74 4y ago
        Yes you can look at the lower-end cores from both ISAs and compare. Higher end riscv will come eventually though, it'll take time just like it did for ARM
      - snvzz 4y ago
        There's e.g. the SiFive P650[0], from 2021. SiFive does claim it does outperform Cortex-A77. Cortex-A77 isn't ARM's fastest anymore, but it was in 2019. Meaning SiFive was, in 2021, not even 2 years behind. If tracing back to prior generations, you'll see SiFive has been quickly closing the gap. To the point that it wouldn't surprise me if at the next iteration from both companies, SiFive and ARM highest performance cores were on par. What's even more amazing is that SiFive's cores are consistently smaller area and lower power to the ARM cores they have comparable performance to. [0] https://www.sifive.com/cores/performance-p650 https://www.sifive.com/cores/performance-p650 [1] https://www.phoronix.com/image-viewer.php?id=2021&image=sifive_p650_1_lrg https://www.phoronix.com/image-viewer.php?id=2021&image=sifi...
  - crotho 4y ago
    The advantage is not NASA's, but SiFive's, or any other company that wants to make their own chip: they don't have to pay a license. I guess it is NASA's advantage too, because their software shouldn't be tied up with any limited group of license holders. Open ISA is huge. It may not mean open hardware on its own, but it sure as hell opens the door to open hardware in the future. I think there is a chinese CPU in development that is claiming to aim to be the linux of CPUs. Can't remember the name but they were at one of the risc-v conferences recently.
  - SassyThrowaway 4y ago
    I think your question makes a lot of sense in the general case, but in case of NASA it very well might be that they scratched their heads, came up with requirements and found that they don't care about there being an ecosystem of any kind due to special nature of their requirements.
jasonwatkinspdx 4y ago
Yes, it's very likely the people involved in this didn't do 30 seconds worth of googling "what is RISC-V." It's so good they could wait around for our unique insights here. I swear, this place's appetite for empty lowbrow armchair dismissal is very disappointing.
goodpoint 4y ago

deleted 4y ago

[deleted]

You can't launch an ISA into space and expect it to do anything. At some point, hardware has to be designed and built based on that ISA.

babypuncher 4y ago
Nonsense; I printed out a copy of the AGC instruction set reference, stuffed it in one of my model rockets, and it turned into a Saturn V mid-flight.
UltraViolence 4y ago
Then what advantage does it have over ARM or x64? The ISA being open doesn't seem to make any difference at all.
- brucehoult 4y ago
  RISC-V is massively simpler (and smaller silicon and lower energy use) for the same performance. Oh, and significantly smaller code size too, so everything from ROMs to RAM (if code is loaded to RAM) to icache can be sized smaller. The ISA being open source means that if SiFive goes out of business or changes its product lineup, or starts to make buggy stuff, or charge too much ... no matter what happens, the customer is free to find another vendor to make software-compatible chips. As we've found out with ARM this week, even if one company with ARM's highest and most expensive form of license, the Architecture License Agreement (ALA), makes a CPU design they are not allowed to transfer or sell that design to another company that also has an ALA without ARM's explicit permission. Or so ARM claims. Let's see what the courts decide about that.
  - awill 4y ago
    >>RISC-V is massively simpler (and smaller silicon and lower energy use) for the same performance. Per my understanding RISC-V has nothing even close performance-wise to Arm's high-end stuff. So isn't it apples to oranges?
    - justahuman74 4y ago
      Yes you can look at the lower-end cores from both ISAs and compare. Higher end riscv will come eventually though, it'll take time just like it did for ARM
    - snvzz 4y ago
      There's e.g. the SiFive P650[0], from 2021. SiFive does claim it does outperform Cortex-A77. Cortex-A77 isn't ARM's fastest anymore, but it was in 2019. Meaning SiFive was, in 2021, not even 2 years behind. If tracing back to prior generations, you'll see SiFive has been quickly closing the gap. To the point that it wouldn't surprise me if at the next iteration from both companies, SiFive and ARM highest performance cores were on par. What's even more amazing is that SiFive's cores are consistently smaller area and lower power to the ARM cores they have comparable performance to. [0] https://www.sifive.com/cores/performance-p650 https://www.sifive.com/cores/performance-p650 [1] https://www.phoronix.com/image-viewer.php?id=2021&image=sifive_p650_1_lrg https://www.phoronix.com/image-viewer.php?id=2021&image=sifi...
- crotho 4y ago
  The advantage is not NASA's, but SiFive's, or any other company that wants to make their own chip: they don't have to pay a license. I guess it is NASA's advantage too, because their software shouldn't be tied up with any limited group of license holders. Open ISA is huge. It may not mean open hardware on its own, but it sure as hell opens the door to open hardware in the future. I think there is a chinese CPU in development that is claiming to aim to be the linux of CPUs. Can't remember the name but they were at one of the risc-v conferences recently.
- SassyThrowaway 4y ago
  I think your question makes a lot of sense in the general case, but in case of NASA it very well might be that they scratched their heads, came up with requirements and found that they don't care about there being an ecosystem of any kind due to special nature of their requirements.

jasonwatkinspdx 4y ago

Yes, it's very likely the people involved in this didn't do 30 seconds worth of googling "what is RISC-V." It's so good they could wait around for our unique insights here. I swear, this place's appetite for empty lowbrow armchair dismissal is very disappointing.

goodpoint 4y ago