6 ms·

From my understanding the Line 6 Helix uses two 450MHz SHARC processors, ADSP-21469. Other effect/amp modelers use more or newer of the same family[0]. Can any

From my understanding the Line 6 Helix uses two 450MHz SHARC processors, ADSP-21469. Other effect/amp modelers use more or newer of the same family[0]. Can anyone comment about the relative processing power of a RPi vs the market solutions? Is the RPi theoretically good enough that a pedalboard could be completely modelled? [0] Interestingly, it sounds like SHARC chips were designed to be low cost processors for single use applications in guided artillery shells.

unwind 4y ago
According to Analog's product page [1] for the ADSP-21469, it delivers 2.7 GFLOPS at 450 MHz. And Wikipedia's page of all the RPi models says that the latest (4B) manages 8 GFLOPS at around 1.8 GHz. If that means that the answer to your question is "yes" or "no" is unfortunately a lot harder to Google and/or figure out. I would assume that the SHARC-based devices run on the metal, whereas most applications for the Raspberry Pi run under Linux, for instance. [1]: https://www.analog.com/en/products/adsp-21469.html#product-overview https://www.analog.com/en/products/adsp-21469.html#product-o... [2]: https://en.wikipedia.org/wiki/Raspberry_Pi#Simplified_Model_B_changelog https://en.wikipedia.org/wiki/Raspberry_Pi#Simplified_Model_... Edit: grammarish.
- renewedrebecca 4y ago
  I'd love to see one of these Raspberry Pi guitar FX projects run on bare metal or a RTOS instead of Linux.
- prima-facie 4y ago
  There's also a real-time version of the Linux kernel which is meant for exactly this type of application.
  - rerdavies 4y ago
    Most of the real-time Linux kernel has been ported into mainline. Mainline is perfectly capable of producing stable low-latency audio, as long as you're running on threads with real-time priority. The real-time kernel provides additional improvements. But it's incredibly difficult to find up-to-date real-time kernels these days.
    - rerdavies 4y ago
      Also worth mentioning that there are enormous USB audio improvements in kernel version 5.10.0, both for performance, stability, and compatibility. As far as I know, there are no real-time kernels available for Pi 4 with a kernel version greater than 5.10.0, and building one is painfully difficult.
bluGill 4y ago
Generally this type of work is done on DSPs and FPGAs, because they can generally get much lower latency than a CPU. While this can get latency low enough that nobody will notice, it is still there, and there isn't room for anything else in your signal chain to also have latency and still be unnoticed. They will still have a CPU on devices like this, but all it does is run the UI, the sound processing is not done on a CPU.
- rerdavies 4y ago
  Why would a DSP be able to get lower latency that a modern general purpose processor? DSPs might have been a thing 15 or 20 years or 30 years ago; but I cannot imagine anything that a DSP would do better than a modern ARM processor.

unwind 4y ago

According to Analog's product page [1] for the ADSP-21469, it delivers 2.7 GFLOPS at 450 MHz. And Wikipedia's page of all the RPi models says that the latest (4B) manages 8 GFLOPS at around 1.8 GHz. If that means that the answer to your question is "yes" or "no" is unfortunately a lot harder to Google and/or figure out. I would assume that the SHARC-based devices run on the metal, whereas most applications for the Raspberry Pi run under Linux, for instance. [1]: https://www.analog.com/en/products/adsp-21469.html#product-overview https://www.analog.com/en/products/adsp-21469.html#product-o... [2]: https://en.wikipedia.org/wiki/Raspberry_Pi#Simplified_Model_B_changelog https://en.wikipedia.org/wiki/Raspberry_Pi#Simplified_Model_... Edit: grammarish.

renewedrebecca 4y ago
I'd love to see one of these Raspberry Pi guitar FX projects run on bare metal or a RTOS instead of Linux.
prima-facie 4y ago
There's also a real-time version of the Linux kernel which is meant for exactly this type of application.
- rerdavies 4y ago
  Most of the real-time Linux kernel has been ported into mainline. Mainline is perfectly capable of producing stable low-latency audio, as long as you're running on threads with real-time priority. The real-time kernel provides additional improvements. But it's incredibly difficult to find up-to-date real-time kernels these days.
  - rerdavies 4y ago
    Also worth mentioning that there are enormous USB audio improvements in kernel version 5.10.0, both for performance, stability, and compatibility. As far as I know, there are no real-time kernels available for Pi 4 with a kernel version greater than 5.10.0, and building one is painfully difficult.

bluGill 4y ago

Generally this type of work is done on DSPs and FPGAs, because they can generally get much lower latency than a CPU. While this can get latency low enough that nobody will notice, it is still there, and there isn't room for anything else in your signal chain to also have latency and still be unnoticed. They will still have a CPU on devices like this, but all it does is run the UI, the sound processing is not done on a CPU.

rerdavies 4y ago
Why would a DSP be able to get lower latency that a modern general purpose processor? DSPs might have been a thing 15 or 20 years or 30 years ago; but I cannot imagine anything that a DSP would do better than a modern ARM processor.