The 486 CPU is considerably of a relic lately, however its legacy within the Linux kernel has lived on. The i486 has been the de facto minimal for many years. Even Linux, that long-term supporter of outdated architectures, is contemplating giving up on the chip and eradicating assist for the 486 processors, similar to it did for the 386 again in 2012.
The information comes through a put up on the Linux Kernel Mailing Checklist (opens in new tab) from Linus Torvalds himself. Lately eager on including issues just like the Rust programming language (opens in new tab)and assist for Intel Arc GPUs and Loongson CPUs (opens in new tab) to the Linux kernel, Torvalds is now contemplating eradicating the venerable 486, writing: “We removed i386 assist again in 2012. Possibly it is time to eliminate i486 assist in 2022?”
The thought, which appears so apparent in lately of Raptor Lake and Ryzen 7000, obtained a certain quantity of pushback, with the declare from some customers that new {hardware} primarily based on the superannuated silicon was nonetheless being shipped. When the identical plan was raised a 12 months in the past, one person stated they have been nonetheless utilizing a 486, and wished to proceed doing so.
The 486, which dates again to 1989, is at present the minimal attainable spec for operating Linux, and works greatest with light-weight distros similar to Tiny Core Linux (opens in new tab).
All of it comes all the way down to cmpxchg8b, an instruction that compares then exchanges eight bytes (or 64 bits) of knowledge within the laptop’s reminiscence. Mailing listing member Peter Zijlstra urged Linux ought to solely assist processors able to carrying this out, leaving the 32-bit 486 behind and that means new Linux kernels would run on P5-class {hardware} or newer. The cmpxchg8b instruction is the perpetrator behind the unique Pentium’s ‘F00F’ bug, which noticed an affected CPU with out working system mitigations in place stop to perform till it was rebooted when requested to execute the instruction.
Kernel 6.1, out this 12 months, might be a Lengthy Time period Help kernel, however with Torvalds’ backing to the concept it could possibly be the final one that can run on the 486, with 6.2 eradicating the power to run Linux on historical beige 486 towers.