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A few days ago the news broke that Intel introduced a simplified x86S processor architecture (x86 simplification) which implements only 64-bit mode and does not support legacy concepts.
With this new x86S architecture, Intel drops support for 16-bit and 32-bit operating systems, but it is mentioned that se can run through virtualization, so the ability to run 32-bit applications in a 64-bit operating system environment will be maintained.
The long life of Intel® architecture has resulted in a rich software ecosystem with a huge installed base that spans from PCs to the cloud, to mobile devices, and from embedded devices to supercomputers and beyond.
Since its introduction more than 20 years ago, Intel® 64 architecture has become the dominant operating mode. As an example of this evolution, Microsoft stopped shipping the 32-bit version of its Windows 11 operating system. Intel's firmware no longer supports non-UEFI64 operating systems natively. 64-bit operating systems are the de facto standard today. They retain the ability to run 32-bit applications, but have stopped supporting 16-bit applications natively.
The processors with the new architecture will immediately start in 64-bit mode, bypassing the intermediate switch to 16-bit and 32-bit modes during the initialization process. x86S also implements the ability to switch to using a 5-level memory page table structure, without first disabling paging and bypassing the transition to pageless mode.
Intel 64 architecture designs come out of the reboot 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 by modern applications or operating systems.
A 64-bit only mode architecture will require 64-bit equivalents of technologies that currently run in real mode or protected mode.
Of the x86S architecture features, the following stand out:
- End of support for 16-bit addressing and the ability to redefine the size of the address.
- Use of a simplified 64-bit memory segment addressing model to support segment addressing in 32-bit applications, which is consistent with the practice used in modern operating systems.
- Drops support for 1 and 2 guard rings, which are not used in modern software.
- End of support for 32-bit mode in ring zero guard.
- Removal of 16-bit and 32-bit protected modes.
- Termination of support for access to I/O ports from the 3rd ring of protection.
- End of support for string operations with input/output ports (INS/OUTS)
- End of support for 8259 interrupt controllers and use of X2APIC programmable controllers only.
- Removes some unused operating system mode bits.
It is worth mentioning that for Intel, maintaining such old hardware requirements can have a severe andn the microarchitecture and design of a device. For example, improvements to startup and code execution cannot be integrated if they have a negative impact on backward compatibility.
Another point is that the devices that rrequire backwards compatibility must dedicate space to old hardware, something that could be better utilized by newer hardware accelerators and runtime systems. It is also highly likely that the use of backward compatibility will also have broader implications for the hardware used in modern designs.
In addition, it is also mentioned that maintaining compatibility with previous versions can also cause security vulnerabilities to persist in new designs. This is especially true during the boot process, where legacy systems may not use strong security practices, allowing any malicious code to run.
Finally, it is mentioned that the transition would not completely remove legacy operating system support. As the company states in a post, Intel has matured virtualization techniques that could still allow legacy software to boot.
If you are interested in knowing more about it, you can check the details In the following link.