It’s finally time: a patch queued into one of the development branches ahead of the upcoming Linux 7.1 merge window is set to finally begin the process of phasing out and ultimately removing Intel 486 CPU support from the Linux kernel. Anyone still using an i486 CPU with an upstream Linux kernel would be incredibly rare and no known Linux distribution vendors are still shipping with i486 CPU support, but in case you are, you can continue to be running one of the existing Linux LTS kernel versions.
Linus Torvalds recently commented that he’s feeling like it’s time for letting the Linux kernel go of its long-present i486 CPU support as there’s “zero real reason” to keep it around and waste upstream Linux kernel development efforts.
Ingo Molnar took action and authored a patch that initially gets rid of the CONFIG_M486SX, CONFIG_M486, and CONFIG_MELAN Kconfig build options. It’s that patch that looks destined for merging in Linux 7.1 so users will no longer be able to build an i486 kernel image. After that in a following kernel series, the actual i486 CPU support code can be gutted to lower the maintenance burden moving forward.
Ingo Molnar remarked with the patch that maintaining the “ancient” 32-bit CPU support requires “various complicated hardware emulation facilities on x86-32” and that compatibility code does induce ongoing maintenance challenges for kernel maintainers. So initially the Kconfig options are being dropped and then barring any complaints, the i486 support can be later gutted.
The M486SX Kconfig option is for 486-class CPUs without an FPU like the AMD/Cyrix/IBM/Intel SL/SLC/SLC2/SLC3/SX/SX2 and UMC U5S. The M486 Kconfig option is for 486-class CPUs such as the AMD/Cyrix/IBM/Intel 486DX/DX2/DX4 and UMC U5D. Lastly the MELAN option is for the AMD Elan processor.
The patch made it this week into tip/tip.git’s “x86/platform” Git branch. With the Kconfig removal part of a TIP branch ahead of the Linux 7.1 merge window later this month, it should be submitted for that merge window. Given that Torvalds already has shown interest in removing i486 support, it’s time to say farewell to the possibility of running a modern upstream Linux kernel version on these very old processors.
