4 ms·

I would’ve thought the two teams worked very close together and had some skill overlap, so that’s surprising

saagarjha 5y ago
There’s definitely overlap once the chip is finished and the software teams start writing software for it, but in early development you’re still trying it make sure the hardware isn’t broken so it doesn’t make sense to involve XNU when you can just test with Linux.
- imwillofficial 5y ago
  Is this assumption or known fact? I’d love to read more
  - cartor 5y ago
    hi, i can chime in and say this is a known fact. M1 is not OOTB IBM PC compatible (unlike almost all x86), which means no standard BIOS/UEFI firmware interface for bootloaders like grub etc. internally, there was some significant overhauls to the automated testing and silicon validation/quality control processes during development (well before pandemic) which resulted in a need for this. apple can validate their silicon, but foundries, factories and other third parties are typically not able to (without added cost, implementation, Apple intellectual property, etc), so developing this was cost beneficiary to apple and eases production, and is really just accordance with existing industry standards for CPU manufacturing. i am just surprised this was made public, the motive i do not know, but i hope this helps explain, it's my first comment on this site.
    - dagmx 5y ago
      Asahi Linux isn't an Apple produced product. It's a third party reverse engineered product
      - cartor 5y ago
        correct, i forgot some context about what i meant "apple developing", apple allowed raw images to be used now, this is what i described being used in the cpu manufacturing process for testing units. this was not always an option. i meant this pseudo-feature being made public, not asahi which has been public and apple has been aware of for over a year see here: [1]: https://github.com/AsahiLinux/m1n1/commit/0d4fb00ceb8a14f08339c443458c5f6b7adb5a23 https://github.com/AsahiLinux/m1n1/commit/0d4fb00ceb8a14f083... [2]: https://news.ycombinator.com/item?id=29591578 https://news.ycombinator.com/item?id=29591578
        marcan_42 5y ago
        The raw image support has nothing to do with silicon bring-up. That is an option for a userspace tool running in macOS recovery mode. At that point you're well past silicon bring-up. I don't know why people keep conflating those two things... it doesn't make any sense whatsoever. Silicon bring-up would happen via iBoot on completely unlocked chips (no secureboot fuses). The raw image mode was added for us. Apple has absolutely zero use for such an option.
        my123 5y ago
        Internally, Apple uses a totally different mechanism to boot Linux, with the silicon validation firmware stack (that runs OpenFirmware of all things) chainloaded from iBoot.
  - GoOnThenDoTell 5y ago
    Ive also heard about linux early-bringup from former apple employees. Obviously what I say isn't proof though
    - Sirened 5y ago
      It also wouldn't surprise me at all that they do this given the sheer complexity of booting XNU on an Apple SoC. XNU _requires_ that it can talk to a bunch of hardware early in boot (which, for what its worth, is partially why booting XNU on non-Apple platforms is such a pain in the ass!), and unless you want to run the entire SoC on FPGAs for the _entire_ development process, you need a kernel that can make due with just a single lonely CPU core and nothing else. Linux is designed to run on everything, and XNU is designed to just run on an Apple SoC.
- dagmx 5y ago
  Wouldn't you also need to get Linux working first though? Like why would Linux be easier than XNU?
  - cartor 5y ago
    the short answer is linux follows standards, and is universal within the engineering teams responsible; far less effort to get working. big thing is that it's easier to "hire talent and hit ground running" in regards to progress

There’s definitely overlap once the chip is finished and the software teams start writing software for it, but in early development you’re still trying it make sure the hardware isn’t broken so it doesn’t make sense to involve XNU when you can just test with Linux.

imwillofficial 5y ago
Is this assumption or known fact? I’d love to read more
- cartor 5y ago
  hi, i can chime in and say this is a known fact. M1 is not OOTB IBM PC compatible (unlike almost all x86), which means no standard BIOS/UEFI firmware interface for bootloaders like grub etc. internally, there was some significant overhauls to the automated testing and silicon validation/quality control processes during development (well before pandemic) which resulted in a need for this. apple can validate their silicon, but foundries, factories and other third parties are typically not able to (without added cost, implementation, Apple intellectual property, etc), so developing this was cost beneficiary to apple and eases production, and is really just accordance with existing industry standards for CPU manufacturing. i am just surprised this was made public, the motive i do not know, but i hope this helps explain, it's my first comment on this site.
  - dagmx 5y ago
    Asahi Linux isn't an Apple produced product. It's a third party reverse engineered product
    - cartor 5y ago
      correct, i forgot some context about what i meant "apple developing", apple allowed raw images to be used now, this is what i described being used in the cpu manufacturing process for testing units. this was not always an option. i meant this pseudo-feature being made public, not asahi which has been public and apple has been aware of for over a year see here: [1]: https://github.com/AsahiLinux/m1n1/commit/0d4fb00ceb8a14f08339c443458c5f6b7adb5a23 https://github.com/AsahiLinux/m1n1/commit/0d4fb00ceb8a14f083... [2]: https://news.ycombinator.com/item?id=29591578 https://news.ycombinator.com/item?id=29591578
      - marcan_42 5y ago
        The raw image support has nothing to do with silicon bring-up. That is an option for a userspace tool running in macOS recovery mode. At that point you're well past silicon bring-up. I don't know why people keep conflating those two things... it doesn't make any sense whatsoever. Silicon bring-up would happen via iBoot on completely unlocked chips (no secureboot fuses). The raw image mode was added for us. Apple has absolutely zero use for such an option.
        my123 5y ago
        Internally, Apple uses a totally different mechanism to boot Linux, with the silicon validation firmware stack (that runs OpenFirmware of all things) chainloaded from iBoot.
- GoOnThenDoTell 5y ago
  Ive also heard about linux early-bringup from former apple employees. Obviously what I say isn't proof though
  - Sirened 5y ago
    It also wouldn't surprise me at all that they do this given the sheer complexity of booting XNU on an Apple SoC. XNU _requires_ that it can talk to a bunch of hardware early in boot (which, for what its worth, is partially why booting XNU on non-Apple platforms is such a pain in the ass!), and unless you want to run the entire SoC on FPGAs for the _entire_ development process, you need a kernel that can make due with just a single lonely CPU core and nothing else. Linux is designed to run on everything, and XNU is designed to just run on an Apple SoC.
dagmx 5y ago
Wouldn't you also need to get Linux working first though? Like why would Linux be easier than XNU?
- cartor 5y ago
  the short answer is linux follows standards, and is universal within the engineering teams responsible; far less effort to get working. big thing is that it's easier to "hire talent and hit ground running" in regards to progress