Intel x86S: a 64-bit-only architecture in detail

Written by Guillaume
Publication date: {{ dayjs(1685376005*1000).local().format("L").toString()}}
This article is an automatic translation

Pushed by AMD, Intel switched to 64-bit on consumer products almost 20 years ago. The opportunity for a (small) upheaval?

Today, many PC users have already switched to 64-bit architecture. In the case of video game enthusiasts, for example, this has virtually become an obligation. Indeed, 32-bit operating systems are unable to support more than 4 GB of RAM, and this amount of RAM is largely insufficient for the majority of productions, while the biggest development studios even require a minimum of 16 GB. However, this is not yet the case for everyone and, more importantly, support for 32-bit architecture is still on the agenda, if only for the sake of backward compatibility.

A situation that could soon change, however, if we are to believe technical documents recently published by Intel, one of the giants of the sector. The originator of the famous x86 architecture, Intel seems to be planning its evolution towards "x86S". As its name suggests, the aim of such an architecture would not be to revolutionize the x86, of which it would be a direct descendant, but rather to lighten it of all that Intel today considers unnecessary and, in particular, support for the old 16-bit and 32-bit modes with the aim, in particular, of speeding up everything to do with booting. Indeed, without the need to check 16/32-bit inheritance, a system could then boot up more quickly, especially as these steps - in addition to being virtually useless - are among the most time-consuming.

Among the improvements Intel expects to see with its x64S architecture are : use of the simplified 64-bit segmentation model to support the segmentation of 32-bit applications, corresponding to what modern operating systems already use, elimination of rings 1 and 2 (unused by modern software) and obsolete segmentation functionalities, elimination of support for 16-bit addressing, elimination of support for I/O port accesses in ring mode 3, elimination of chain port I/O, limitation of the use of the local interrupt controller (APIC) to X2APIC and elimination of support for the old 8259 model.

Of course, with such a change in architecture, there's no question of Intel removing the ability to run 32-bit applications on a 64-bit operating system. This would make no sense given current needs and habits. Intel is very clear on this point, stating that " the 32-bit sub-mode of Intel64 (compatibility mode) is still present ". The main aim of the new x86S architecture is to prevent the start-up of non-64-bit operating systems, precisely in order to speed things up on such systems. For the majority of users - who have already switched to a 64-bit OS - this change will be painless, and we can even assume that they won't notice a thing. To find out more about this architecture, we suggest you read the technical documents published by Intel. Please note that the PDF file is 46 pages long!