Intel proposed a series of changes to the x86 processor architecture to adapt it to modern realities and abandon end-to-end backwards compatibility. The company released a specification for a simplified x86S architecture with no support for 16- and 32-bit operating systems – only 64-bit.
Modern x86 processors are capable of supporting all the features that every previous CPU generation offered, starting with the Intel 8086 released in 1978. However, according to Intel, this is not necessary: nobody uses operating systems that were made a few decades ago published. In addition, the environment can be emulated for them by replacing the missing hardware features with virtualization technologies. Therefore, full x86 compatibility only complicates the design of processors, but does not bring any practical benefits. This allows the architecture to be simplified and made more efficient – this idea is anchored in the x86S.
At the same time, the well-known 64-bit mode should become the main mode for x86S processors. This avoids the switch from initial 16-bit to 32-bit and then to 64-bit mode that modern x86 processors go through on every boot. As a result, x86S processors lose compatibility with 16-bit and 32-bit operating systems, but there is no special need for this – Windows 11, for example, does not have a 32-bit version at all. The performance of 32-bit applications remains the same – they are launched in “compatibility mode” of 64-bit operating systems as before.
The main innovations in the x86S architecture described in the Intel document include: the deprecation of support for 16-bit addressing; Starting the processor immediately in 64-bit mode; work exclusively with 64-bit UEFI; Elimination of the first and second protection rings, which are unnecessary for modern operating systems; disable access to I/O ports from the third protection ring; abort string operations with I/O ports; Discontinuation of the interrupt controller 8259; as well as the ability to run legacy operating systems solely through emulation.
The last major change to the x86 architecture – the addition of 64-bit registers and x86-64 modes – was implemented at the initiative of AMD, which made a corresponding proposal in 1999. The company’s first x86-64 processor appeared in 2003, and Intel didn’t add support for 64-bit applications until 2004. But this time, Intel decided to act as the engine of progress and not give the competitor the initiative to initiate long-overdue transformations.
However, the appearance of a detailed x86S specification in no way means that Intel will start large-scale implementation in the near future. However, it is obvious that work is being done in this direction, and engineers are looking for ways to simplify and improve the performance of future processors, including through changes to the basic functionality. According to Intel, the transition to the x86S architecture will be a logical step after the elimination of the A20 address line in 2008 (which allowed the Intel 8086 processors to address up to 1 MB of memory) and the recent elimination of support for 16- and 32-bit Bit operating systems at the BIOS level of motherboards. .