Linus Benedict Torvalds is a Finnish-American software engineer, known for starting and maintaining the development of the Linux kernel,
Recently while discussing solutions on x86 processors that don't support The instruction «cmpxchg8b», Linus Torvalds stated that it might be time to make this statement mandatory for the kernel to run and remove support for i486 processors that don't support "cmpxchg8b", rather than "trying to emulate how" this instruction works on processors that "nobody uses anymore".
Currently, almost all Linux distributions that continue to support x86 32-bit systems have switched to compiling the kernel with the X86_PAE option, which requires "cmpxchg8b" support.
According to Linus, in terms of support in the kernel, i486 processors have lost relevance, even though they are still found in everyday life. At a certain point, processors become museum pieces, and for them it is quite possible to get by with "museum" cores.
It is worth mentioning that if the removal of support for the classic i486 proceeds, this will not affect Intel's embedded Quark processors, which, although they belong to the i486 class, include additional instructions typical of the Pentium generation, including "cmpxchg8b ».
In addition to that it is mentioned that the same applies to Vortex86DX processors. Support for i386 processors was dropped in the kernel 10 years ago.
Maybe we should bite the bullet and say that we only support x86-32 with 'cmpxchg8b' (ie Pentium and later).
Get rid of all the "emulate 64-bit atomics with cli/sti, knowing no one has SMP on those CPUs anyway", and implement a generic x86-32 xchg() setup using that try_cmpxchg64 loop.
I think most (all?) distributions already enable X86_PAE anyway, which makes X86_CMPXCHG64 part of the base requirement.
Not that I'm convinced that most distributions even do 32-bit development these days.
...
We got rid of i386 support in 2012. Maybe it's time to drop i486 support in 2022?
The end of support for i486 could be a milestone to consider, since not long ago various Linux distributions chose to eliminate support for 32-bit processors, which did not really have the repercussions many expected. Since as such yes, there are still thousands of users who have low-resource computers, which made Linux an excellent option to continue using them, especially in many marginalized areas.
And although support for this type of equipment continued to be given by the main distributions, their current requirements made their use impossible to carry out. The truth is that there are still some distributions that continue to support this architecture and, above all, that are optimized for the use of low-resource computers.
Regarding the case of end of support, it is mentioned that the users who have systems with i486 processors will be able to use the LTS versions of the kernelwhich will last for many years to come.
On the other hand, it is also worth mentioning that the Linux driver developer open source for Apple AGX GPU used in the Apple M1 chips reported that successfully passed 99,3% of the dEQP-GLES2 suite tests, which verifies the level of support for the OpenGL ES 2 specification. Two components were used in the work: a DRM driver for the Linux kernel, written in Rust, and a Mesa driver written in C.
The development of controllers is complicated by the fact that Apple M1 uses its own GPU, designed by Apple, runs proprietary firmware and uses fairly complex shared data structures. There is no technical documentation for the GPU, and independent driver development uses reverse engineering of macOS drivers.
The controller open source developed for Mesa was initially tested in a macOS environment until the DRM (Direct Rendering Manager) driver required for the Linux kernel was prepared, which allowed the driver developed for Mesa to be used on Linux.
In addition to the current success in passing the dEQP-GLES2 tests, in late September the Linux driver for Apple M1 chips reached a level suitable for running a Wayland-based GNOME session and running the game Neverball and YouTube in the Firefox browser.
Finally if you are interested in knowing more about it, you can check the details in the following link