The Linux kernel 6.15 is in the works for a stable release. A preliminary version of Release candidate 5 was released over the weekend; the final release is expected in late May or early June. This will be a significant update, as it will remove support for Intel’s 80486-era processors.
Image source: Procreator / unsplash.com
The change was made by veteran kernel developer Ingo Molnar, and will remove nearly 15,000 lines of code from the platform. The kernel will gain mandatory support for some features, including TSC (Timer Stamp Counter) and the CMPXCHG8B (Compare and Exchange 8 Bytes) instruction; it will also lose support for processors older than the first Intel Pentium, i.e. the Intel i486 family and some related early 586 processors, including the IDT WinChip and AMD Elan series. Linux will no longer support the 485slc processors, which were essentially 386SX with additional instructions from the 80486 series.
Thus, Linux 6.15 will effectively lose support for the latest x86 chips that did not have built-in floating-point units (FPUs); the kernel will be able to refuse support for FPU emulation in software. Notably, FPU emulation returned to the NetBSD 10 codebase in February. The last time Linux lost support for older processors was quite a long time ago: in 2012, the kernel lost the ability to work with 386 chips. Linus Torvalds proposed to abandon support for i486 back in 2022, but the proposal was rejected at the time.