Intel has actively started investigating enhancements that future x86S architectures would bring with 64-bit-only solutions.

Future Intel Architectures To Focus Solely on x86S 64-bit Mode-Only Designs

The Intel 64 architecture has been around for over 20 years & due to its widespread use, Microsoft entirely dropped 32-bit versions of its latest operating system. Currently, Intel's firmware no longer supports non-UEFI64 operating systems natively but they do carry some form of legacy support to run 32-bit applications where there's a need. However, as the company moves forward, Intel is now proposing a brand new architecture which is referred to as x86S and is basically a 64-bit mode-only architecture that removes all previous legacy support.

How Would a 64-Bit Mode-Only Architecture Work?

Intel® 64 architecture designs come out of reset in the same state as the original 8086 and require a series of code transitions to enter 64-bit mode. Once running, these modes are not used in modern applications or operating systems.

An exclusively 64-bit mode architecture will require 64-bit equivalents of technologies that currently run in either real mode or protected mode. For example:

Booting CPUs (SIPI) starts in real-address mode today and needs a 64-bit replacement. A direct 64-bit reset state eliminates the several stages of trampoline code to enter 64-bit operation.Today, using 5-level pages requires disabling paging, which requires going back to unpaged legacy mode. In the proposed architecture, it is possible to switch to 5-level paging without leaving a paged mode.

These modifications can be implemented with straightforward enhancements to the system architecture affecting the operating system only.

What Would Be the Benefits of a 64-bit Mode-Only Architecture?

A 64-bit mode-only architecture removes some older appendages of the architecture, reducing the overall complexity of the software and hardware architecture. By exploring a 64-bit mode-only architecture, other changes that are aligned with modern software deployment could be made. These changes include:

Using the simplified segmentation model of 64-bit for segmentation support for 32-bit applications, matching what modern operating systems already use.Removing ring 1 and 2 (which are unused by modern software) and obsolete segmentation features like gates.Removing 16-bit addressing support.Eliminating support for ring 3 I/O port accesses.Eliminating string port I/O, which supported an obsolete CPU-driven I/O model.Limiting local interrupt controller (APIC) use to X2APIC and removing legacy 8259 support.Removing some unused operating system mode bits.

Legacy Operating Systems on 64-Bit Mode-Only Architecture

While running a legacy 64-bit operating system on top of a 64-bit mode-only architecture CPU is not an explicit goal of this effort, the Intel architecture software ecosystem has sufficiently matured with virtualization products so that a virtualization-based software solution could use virtualization hardware (VMX) to deliver a solution to emulate features required to boot legacy operating systems.

News Source: Bionic_squash