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> You can definitely get a license that allows you to go hog wild and make breaking changes. I believe both Apple and Google pay for that. Reference?

my123 5y ago
There is some minor breakage, like Apple CPUs enforcing the VHE feature of ARMv8.1-A to be on, and not supporting it being off. But that was like… the sole issue on that front. What you are allowed to do is make extensions with the highest tier of arch licenses, you however cannot break the ISA.
- klelatti 5y ago
  Thanks! Very interesting on VHE.
- saagarjha 5y ago
  VHE isn't even observable for userspace code, and Apple is very quickly going to drop support for people being in the kernel, so I would argue this probably isn't even that important.
  - my123 5y ago
    For macOS at Reduced Security, kernel extensions will no longer be supported. fuOS/CustomKC will stay in the long term, and that's what matters for other OSes.
deleted 5y ago
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Cyph0n 5y ago
It’s called an architectural license. There are a few publicly announced license holders, including Apple and Qualcomm. Refer to the Arm wiki page for a list. Probably outdated article on this: https://www.electronicsweekly.com/news/business/finance/arm-adds-architectural-licensee-2015-04/ https://www.electronicsweekly.com/news/business/finance/arm-...
- klelatti 5y ago
  > Companies can also obtain an ARM architectural licence for designing their own CPU cores using the ARM instruction sets. These cores must comply fully with the ARM architecture. (Wikipedia) That's not going 'hog wild'!
szundi 5y ago
Does not need a reference as ARM itself is not the whole platform that can be compatible or incompatible. Whoever tried to change CPU/microcontroller finds that not the core itself that matters the most, but the peripherals and the whole stuff as a system.
- klelatti 5y ago
  We’re talking about licences for Arm cores.

my123 5y ago

There is some minor breakage, like Apple CPUs enforcing the VHE feature of ARMv8.1-A to be on, and not supporting it being off. But that was like… the sole issue on that front. What you are allowed to do is make extensions with the highest tier of arch licenses, you however cannot break the ISA.

klelatti 5y ago
Thanks! Very interesting on VHE.
saagarjha 5y ago
VHE isn't even observable for userspace code, and Apple is very quickly going to drop support for people being in the kernel, so I would argue this probably isn't even that important.
- my123 5y ago
  For macOS at Reduced Security, kernel extensions will no longer be supported. fuOS/CustomKC will stay in the long term, and that's what matters for other OSes.

deleted 5y ago

[deleted]

Cyph0n 5y ago

It’s called an architectural license. There are a few publicly announced license holders, including Apple and Qualcomm. Refer to the Arm wiki page for a list. Probably outdated article on this: https://www.electronicsweekly.com/news/business/finance/arm-adds-architectural-licensee-2015-04/ https://www.electronicsweekly.com/news/business/finance/arm-...

klelatti 5y ago
> Companies can also obtain an ARM architectural licence for designing their own CPU cores using the ARM instruction sets. These cores must comply fully with the ARM architecture. (Wikipedia) That's not going 'hog wild'!

szundi 5y ago

Does not need a reference as ARM itself is not the whole platform that can be compatible or incompatible. Whoever tried to change CPU/microcontroller finds that not the core itself that matters the most, but the peripherals and the whole stuff as a system.

klelatti 5y ago
We’re talking about licences for Arm cores.