5 ms·

> The CPU emulator, ARMeilleure, emulates an ARMv8 CPU and currently has support for most 64-bit ARMv8 and some of the ARMv7 (and older) instructions, including

> The CPU emulator, ARMeilleure, emulates an ARMv8 CPU and currently has support for most 64-bit ARMv8 and some of the ARMv7 (and older) instructions, including partial 32-bit support. It translates the ARM code to a custom IR, performs a few optimizations, and turns that into x86 code. Interesting... since .Net is cross-platform and can run on ARM, if it's running on an ARM processor does it just run the instructions directly?

calaphos 6y ago
The current ARMeilleure seems to emit x86 instructions directly and execute them, so never really using the intermediate representation of Jit compiler of the .Net runtime. However the previous cpu emulator apparently emitted .Net byte code and used RyuJIT (the .Net jit) to emit the final native code. > if it's running on an ARM processor does it just run the instructions directly? So maybe? There are some passes in between but one would think it would at least result in very similar instructions.
- worewood 6y ago
  > However the previous cpu emulator apparently emitted .Net byte code and used RyuJIT (the .Net jit) to emit the final native code. This seems like a good use case for using .Net. Why did they move away from it?
  - astrange 6y ago
    The .NET and Java VMs probably aren't optimized for the incoming bytecode also being JIT generated, never needing to allocate memory, wanting to be register-based, etc. Also, I haven't tried JITting them but I've always found their bytecodes to be pretty inexpressive compared to a real CPU (or even LLVM).
grishka 6y ago
> if it's running on an ARM processor does it just run the instructions directly? You can't just run random instructions like that. That code is compiled with the assumption that there's the Switch's OS and hardware underneath, which means it will do all kinds of things, like calling directly into the kernel and assuming a particular address space layout, that would crash it under a different OS. ARM has hardware virtualization. If the host OS supports it, you should be able to make use of it.
- jyrkesh 6y ago
  I think it does beg the question though, of whether it might be possible to dump the Switch OS and firmware and run it on some alternative ARM hardware (with some modifications for redirecting weird custom chips). IIRC the Switch is running an overclocked Tegra (X1?) IANAL, but in the US at least, I think every person would need to buy their own Switch and dump the software themselves for it to be even remotely legal.
  - astrange 6y ago
    There is a Switch emulator using virtualization on M1 Macs.
    - Wowfunhappy 6y ago
      Wow, that’s neat. Link?
      - saagarjha 6y ago
        https://twitter.com/daeken/status/1340777743244509196 https://twitter.com/daeken/status/1340777743244509196
  - tibbon 6y ago
    I might be making a bad analogy, but I don't think this would work any better than dumping the CMOS firmware for a C64 (6502 processor) and hoping you could just run it on an Apple II or NES, even though they had the same architecture processor (also a 6502). Maybe things are more standard now these days, but the support hardware around it, memory layout, etc... at least for the 6502, made this prohibitive.
  - roblabla 6y ago
    I attempted this a while ago, running the Switch OS (Horizon/NX) on a Jetson TX1. It's definitely possible, *but* it requires modifications to the OS services, otherwise you'll just fry the Jetson (that was a lesson learned the hard way...). The pinmuxing between the two devices is different, so you'd need to modify that at least. And then you'd probably need some more modifications to get joycons to work (how do you sync them without a rail), etc... The kernel however runs absolutely fine with zero modifications required. HorizonOS is a microkernel, and all the components are fairly well separated. To make it work on a jetson, you'd only have to replace a handful of services to make it work. > IANAL, but in the US at least, I think every person would need to buy their own Switch and dump the software themselves for it to be even remotely legal. Honestly, I'm pretty sure it'd violate the DMCA DRM protections in the US (you'd have to dump some crypto keys and provide them to an EL3 reimplementation, like Exosphere, to run anything below the kernel).
molticrystal 6y ago
From https://github.com/Ryujinx/Ryujinx/issues/1884#issuecomment-757136812 https://github.com/Ryujinx/Ryujinx/issues/1884#issuecomment-... : >Rest assured, this is in our long term plan. Initially, we'll be bringing up ARM support as a dynamic code translation target architecture in the short term, as this is a relatively straightforward thing to add to our existing JIT. This work is already underway.

calaphos 6y ago

The current ARMeilleure seems to emit x86 instructions directly and execute them, so never really using the intermediate representation of Jit compiler of the .Net runtime. However the previous cpu emulator apparently emitted .Net byte code and used RyuJIT (the .Net jit) to emit the final native code. > if it's running on an ARM processor does it just run the instructions directly? So maybe? There are some passes in between but one would think it would at least result in very similar instructions.

worewood 6y ago
> However the previous cpu emulator apparently emitted .Net byte code and used RyuJIT (the .Net jit) to emit the final native code. This seems like a good use case for using .Net. Why did they move away from it?
- astrange 6y ago
  The .NET and Java VMs probably aren't optimized for the incoming bytecode also being JIT generated, never needing to allocate memory, wanting to be register-based, etc. Also, I haven't tried JITting them but I've always found their bytecodes to be pretty inexpressive compared to a real CPU (or even LLVM).

grishka 6y ago

> if it's running on an ARM processor does it just run the instructions directly? You can't just run random instructions like that. That code is compiled with the assumption that there's the Switch's OS and hardware underneath, which means it will do all kinds of things, like calling directly into the kernel and assuming a particular address space layout, that would crash it under a different OS. ARM has hardware virtualization. If the host OS supports it, you should be able to make use of it.

jyrkesh 6y ago
I think it does beg the question though, of whether it might be possible to dump the Switch OS and firmware and run it on some alternative ARM hardware (with some modifications for redirecting weird custom chips). IIRC the Switch is running an overclocked Tegra (X1?) IANAL, but in the US at least, I think every person would need to buy their own Switch and dump the software themselves for it to be even remotely legal.
- astrange 6y ago
  There is a Switch emulator using virtualization on M1 Macs.
  - Wowfunhappy 6y ago
    Wow, that’s neat. Link?
    - saagarjha 6y ago
      https://twitter.com/daeken/status/1340777743244509196 https://twitter.com/daeken/status/1340777743244509196
- tibbon 6y ago
  I might be making a bad analogy, but I don't think this would work any better than dumping the CMOS firmware for a C64 (6502 processor) and hoping you could just run it on an Apple II or NES, even though they had the same architecture processor (also a 6502). Maybe things are more standard now these days, but the support hardware around it, memory layout, etc... at least for the 6502, made this prohibitive.
- roblabla 6y ago
  I attempted this a while ago, running the Switch OS (Horizon/NX) on a Jetson TX1. It's definitely possible, *but* it requires modifications to the OS services, otherwise you'll just fry the Jetson (that was a lesson learned the hard way...). The pinmuxing between the two devices is different, so you'd need to modify that at least. And then you'd probably need some more modifications to get joycons to work (how do you sync them without a rail), etc... The kernel however runs absolutely fine with zero modifications required. HorizonOS is a microkernel, and all the components are fairly well separated. To make it work on a jetson, you'd only have to replace a handful of services to make it work. > IANAL, but in the US at least, I think every person would need to buy their own Switch and dump the software themselves for it to be even remotely legal. Honestly, I'm pretty sure it'd violate the DMCA DRM protections in the US (you'd have to dump some crypto keys and provide them to an EL3 reimplementation, like Exosphere, to run anything below the kernel).

molticrystal 6y ago

From https://github.com/Ryujinx/Ryujinx/issues/1884#issuecomment-757136812 https://github.com/Ryujinx/Ryujinx/issues/1884#issuecomment-... : >Rest assured, this is in our long term plan. Initially, we'll be bringing up ARM support as a dynamic code translation target architecture in the short term, as this is a relatively straightforward thing to add to our existing JIT. This work is already underway.