x86S: Intel to create 64-bit only CPUs

[Retro]

Did you know that even the very latest multicore 64-bit x64 CPUs still boot up in the original 16-bit 8086 mode from 1978? They also support 32-bit modes and this is all for compatibility reasons. Well, Intel thinks it's time to finally get rid of this legacy baggage and has released a document proposing the changes for a 64-bit only future called x86S.

What I'd really like to see, is a 128-bit CPU, the next evolution. However, there's no market for them at the moment, but it would be fascinating to see one, of any architecture. It would have a huge pinout too and a smaller core count for a given process node due to the bigger size of the core.

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 remove legacy 8259 support.
Removing some unused operating system mode bits.

Full details here:

Envisioning a Simplified Intel® Architecture

Intel investigated architectural enhancements and modifications for a 64-bit mode-only architecture.

www.intel.com

General info on 128-bit computing:

128-bit computing - Wikipedia

en.wikipedia.org

 

[Retro]

@Geffers you'll like this one.

 

[Geffers]

@Geffers you'll like this one.

The Raspberry Pi foundation are still supporting 32 bit for the time being although Pi devices from 2 onwards are capable of 64 bit.

The current Raspberry Pi OS is available in both 32 and 64 bit versions.

Geffers

 

[Retro]

Note also the primary reason given for going from 32-bit to 64-bit is to widen the address bus. I've never understood this, since the 8-bit 6502 and Z80 CPUs from the 1970s had 16-bit address buses and worked just fine that way, so it should be the same with ARM or x86/64 CPUs.

The main benefit of wider CPU word handling is to make certain calculations faster by 2x as it handles twice as much data at once.

 

[Retro]

Back in May 2023, I started this thread with:

Did you know that even the very latest multicore 64-bit x64 CPUs still boot up in the original 16-bit 8086 mode from 1978?

Now, Inkbox has created a video proving this where he installs 45 year old DOS and then plays 16-bit Doom on it. That's some serious backward compatibility right there. Yes, whatever PC you have, no matter how advanced and modern the CPU is, it will still start up in 8086 16-bit real mode and then the BIOS will switch it into 64-bit mode. That's all of them and that's something worth nerding about.

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[Retro]

The Raspberry Pi foundation are still supporting 32 bit for the time being although Pi devices from 2 onwards are capable of 64 bit.

I've used 32-bit ARM instructions when programming my Archimedes (A3000 strictly speaking) back in the day, but I'd love to see the 64-bit versions in action. Total nerdout, geffers.