Linux Kernels No Longer Compatible With 486 and 586 Processors Due to Recent Updates
In a move aimed at modernising the Linux kernel, version 6.15 will no longer support Intel 486 and early "586" chips. This decision, made by long-time Linux kernel developer Ingo Molnar, is primarily due to housekeeping and technical updates that render the new kernel code incompatible with these very old processors.
The reason behind this change lies in the evolving nature of the Linux kernel. Modern kernel code now requires features such as the Time Stamp Counter (TSC) and CX8 (CMPXCHG8B) hardware instructions, which early 486 and 586 chips do not support. As a result, the removal of older code paths and emulation facilities that were needed to support such legacy hardware simplifies and modernises the kernel, improving maintainability and performance for current architectures.
Linus Torvalds and other maintainers concluded that since these processors are ancient and almost never used anymore, and since no one maintains or tests them, it's more practical to drop support rather than spend time troubleshooting untestable hardware. Users who still want to run Linux on these chips can continue using older kernel versions or patch in support themselves if they have the expertise and hardware.
It's important to note that this decision has been anticipated for some time. The 486 support in the Linux kernel had actually been broken for years, but unnoticed because the hardware is extremely rare and maintainers no longer have the resources or interest to keep it working.
The lack of vocal community opposition in the month or so that the kernel patch has been public indicates a lack of active users for these older processors. Older machines running Linux will still be able to run, just not the most up-to-date kernels.
Intel made its last shipments of i486 chips on September 28, 2007, but these chips weren't for mainstream use beyond the early 1990s. The move reflects a practical choice to focus resources on supporting contemporary hardware.
While it's sad to say goodbye to the 486 and the gaggle of almost-Pentiums from other manufacturers, it's encouraging to see Linux developers continuing to prune the chaff and improve the kernel for the future. After all, technology moves forward, and so must we.
[1] https://lkml.org/lkml/2022/3/16/200 [2] https://lkml.org/lkml/2022/3/24/231 [3] https://lkml.org/lkml/2022/3/29/143
The evolving nature of technology necessitates the adoption of features such as the Time Stamp Counter (TSC) and CX8 hardware instructions, which are incompatible with early Linux hardware like the Intel 486 and 586 chips. Given their obscurity and lack of maintenance, it's more practical for Linux developers to focus on supporting contemporary hardware and drop support for these legacy processors.
