One of the first PCs I came across was equipped with an Intel 486 processor. Representing an era, this family of chips is still supported by Linux today. But it is possible that this will change in the near future. Linus Torvalds already consider remove support for 486 processors from the kernel.
This possibility had already been raised at other times. Last year, for example, the idea was even discussed, but one developer claimed to still have an i486 and Linux-based machine in operation.
The matter was left to one side until, recently, Torvalds brought the idea up again in the kernel mailing list. In one of the interactions, he presents the removal of a component as an indirect solution to a problem in the kernel discussed in the topic. At the end of the message, Torvalds asks:
We stopped supporting i386 in 2012. Maybe it’s time to get rid of i486 support in 2022?
486: iconic but old
i486 and 486 are names that refer to the 80486 chips, released by Intel in the late 1980s. Later, more advanced variations appeared, such as 80486DX and 80486DX2. The market also witnessed the launch of competing alternatives, such as AMD’s Am486 family.
These processors are so old that today it is difficult to find machines based on them in use. Exceptions are for PCs maintained by enthusiasts or by very old applications, but still in operation today.
That’s why Torvalds is considering removing support for the i486 platform from the kernel. In his understanding, this is not important today. On the list, he acknowledged that there might still be interest in support, but argued that “from a kernel development point of view, I don’t think it’s [algo] really relevant”.
If it works, why mess with it?
Removing little (or unused) code can contribute to the performance, maintenance and, above all, the security of the kernel. Not infrequently, the preservation of certain resources requires adaptations in others or requires additional work.
Sometimes the best way to maintain a project as comprehensive as Linux is to cut out the nonessentials rather than following the policy of embracing the world.
This has been done before. As Linus Torvalds recalled in his message, the kernel no longer supports i386 chips (prior to i486, obviously) in 2012.
At the time, he explained that support for the 386 architecture “plagued us with additional work whenever we wanted to change the SMP primitives. [multiprocessamento simétrico]”. The end of i386 support left no injuries, after all.
Here, the idea would be to require the x86 processor to support the cmpxchg8b instruction (used in operations that compare eight-byte information in memory). This means that only Pentium chips and later would be officially supported by Linux.
If the change occurs, it will not be immediately. Currently, the Linux kernel is at version 6.0. The next one, 6.1, may be released in December and, as it is an LTS version (with extended support), it shouldn’t undergo major changes.
Chances are good that the end of i486 support on Linux will happen from kernel 6.2 onwards, therefore.
For those who have 486 computers, the solution is to use a distribution with an old version of the kernel, as Torvalds himself (sarcastically) suggests: “sometimes people have them as museum pieces. They can also run museum kernels.”
With information: Phoronix.