The final version of HP-UX, HP-UX 11i v3, is no longer supported as of the end of 2022, marking the end of a Unix lineage that began in 1982, with the demise driven by the obsolescence of Itanium processors and the shift towards x86 architectures.
Intel's Itanium processors and their IA-64 architecture face another death as Linux support for Itanium is being removed in the upcoming 6.7 release of the Linux kernel. This follows a series of previous setbacks for Itanium, including discontinued improvements, the end of Windows Server updates, and the introduction of AMD's 64-bit processor lineup. The removal of Itanium support in the Linux kernel is due to lack of testing and maintenance. Hewlett-Packard Enterprise will continue to support its last Itanium-based servers until 2025. Additionally, there have been discussions about removing support for Intel's 80486 processors in Linux.
Intel has released a whitepaper proposing the removal of all pre-x86_64 features from x86 CPUs, including 16 and 32-bit modes, rings 1 and 2, and other low-level I/O features. The system would boot straight into 64-bit mode, which Intel believes is what most users use anyway. However, current 64-bit operating systems would not be compatible with this new boot procedure and low-level features. This proposal is reminiscent of Intel's failed Itanium architecture, and it remains to be seen how AMD will respond.