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Envisioning a Simplified Intel Architecture

intel.com

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Re: Envisioning a Simplified Intel Architecture

#41

Post by hinkley »

xorcist wrote: post #31
loeg wrote: post #2

For those truly too lazy to click through to the article, x86-S stands for "simplified," with the idea being to boot directly into 64-bit mode instead of booting into 16-bit and bootstrapping to 64-bit mode. 16-bit mode would be removed entirely. It's not clear to me if 32-bit mode would be axed as well, or if it would be retained (maybe partially).

If I had to list one hundred ways x86 could be improved, not booting in 16-bit mode wouldn't be on it. It's just an incantation. There's no fallout from it. If we're talking firmware, the gigantic mess that used to be called ACPI, still leave users suffering every day for example.

I think that depends on if the existence of 16 bit mode has effects on IPC rates of the processor.

If it's 2% of instruction cost, then kill it with fire. If it's raising the development cost by 1%, kill it with fire. If it's a fixed cost and isn't hurting anything, then meh.

Re: Envisioning a Simplified Intel Architecture

#42

Post by epylar »

dathinab wrote: post #37
r00fus wrote: post #9

Earlier quoted context omitted.

Why? Because it's really just AMD-64?

probably but also it's a stretch in general as for personal computers arm is the dominant platform since years (there are way more phones, tablets, etc. then x86 laptops/desktops by now, all of which fit the original definition of personal computer)

It's saying that the 64-bit mode became dominant over other Intel modes.

Re: Envisioning a Simplified Intel Architecture

#43

Post by bear8642 »

manuelabeledo wrote: post #18
jhallenworld wrote: post #16

Earlier quoted context omitted.

>Legacy systems and architectures can’t be around forever. Why not? The bits don't decay.. Yes, this leads to an architectural mess, but I'm talking about a competitive business advantage.

> Why not? > Yes, this leads to an architectural mess Right there. There's no notable advantage in supporting a very small minority of the applications out there, at the cost of keeping units useless for the 99%.

> There's no notable advantage...

Potentially one if a large customer's paying you for it.

At work, I'm helping a client upgrade from a decade old version (v12) of our product and having to copy over the switches to keep the even older (v11 and previous) behaviours

Re: Envisioning a Simplified Intel Architecture

#44

Post by manuelabeledo »

bear8642 wrote: post #43
manuelabeledo wrote: post #18

Earlier quoted context omitted.

> Why not? > Yes, this leads to an architectural mess Right there. There's no notable advantage in supporting a very small minority of the applications out there, at the cost of keeping units useless for the 99%.

> There's no notable advantage... Potentially one if a large customer's paying you for it. At work, I'm helping a client upgrade from a decade old version (v12) of our product and having to copy over the switches to keep the even older (v11 and previous) behaviours

Ten years ago was 14 years after the introduction of the x86 64-bit instruction set, and 28 years after x86-32.

I’m quite sure we will be OK without support for 16-bit instructions.

Re: Envisioning a Simplified Intel Architecture

#45

Post by snvzz »

userbinator wrote: post #32

Do not want. Did they not learn from the https://en.wikipedia.org/wiki/Intel_80376 or the infamous Itanic? The almost 50 years of backwards compatibility (along with the accompanying creation of a huge amount of documentation) is one of the strongest reasons for choosing the x86/PC. With each feature removal, they weaken that argument and push their (prospective) customers towards reconsidering all the other competit…

>Maybe it's time for a CISC-V...?

I believe the only path forward for x86 is to be a "x86 accelerator", a x86 mode in some future AMD/Intel RISC-V processors, perhaps limited to unprivileged "usermode".

Easing the transition until x86 can be relegated to emulation.

Re: Envisioning a Simplified Intel Architecture

#46

Post by FullyFunctional »

userbinator wrote: post #35
manuelabeledo wrote: post #26

Earlier quoted context omitted.

I wouldn’t say “none”. Real estate in CPUs is extremely expensive.

...and taken up mostly by cache and vector execution units. An 8086 has 29000 transistors. A modern CPU has several billion. The amount needed to implement the 16-bit subset of the ISA is an absolutely tiny fraction of the total area.

Ah, I see you don't work in the field.

A few of the cost of legacy:

* exponential growth in verification space (each feature combines with all other features),

* design complexity (effort that could be spent better),

* area/power/cycle time overhead (all options require more ports to muxes, more wires to run, etc.)

* and most importantly, opportunity costs: some optimization tricks can't be pursued because the assumptions would break for legacy code

The legacy tax is real

Re: Envisioning a Simplified Intel Architecture

#47

Post by glhaynes »

jhallenworld wrote: post #6

This makes no sense to me. Backward compatibility is a huge competitive advantage for Intel, and IMHO, it's royally messed up that vm86 mode doesn't work in 64-bit mode. One DOS application I use was hurt by this: "old DOS OrCAD". It works well in Windows-XP on a 32-bit machine, but does not work at all in 64-bit Windows. (It's actually a 32-bit DPMI program and has drivers to use Windows GDI so you don't have to mes…

and has drivers to use Windows GDI so you don't have to mess around with drivers

This was a thing? So, would it still run in the "MS-DOS Command Prompt" in Windows but talk directly to Windows for its screen drawing?

Re: Envisioning a Simplified Intel Architecture

#48

Post by karmakaze »

kinghajj wrote: post #14
mananaysiempre wrote: post #12

Earlier quoted context omitted.

I guess we should be thankful they aren’t still calling it EM64T :) I’ve also heard that the term AMD64 also originated from marketing—the internal name during development was x86-64 (which everybody but Microsoft ended up calling it anyway).

`amd64` is still what Debian and Kubernetes use.

Apparently, Intel hates that Linux (properly) names the architecture amd64 according to its creator.

Re: Envisioning a Simplified Intel Architecture

#49

Post by NullPrefix »

xorcist wrote: post #31
loeg wrote: post #2

For those truly too lazy to click through to the article, x86-S stands for "simplified," with the idea being to boot directly into 64-bit mode instead of booting into 16-bit and bootstrapping to 64-bit mode. 16-bit mode would be removed entirely. It's not clear to me if 32-bit mode would be axed as well, or if it would be retained (maybe partially).

If I had to list one hundred ways x86 could be improved, not booting in 16-bit mode wouldn't be on it. It's just an incantation. There's no fallout from it. If we're talking firmware, the gigantic mess that used to be called ACPI, still leave users suffering every day for example.

You're judging it from the user's perspective (OS developer). Getting rid of 16-bit mode would probably simplify something for the chip manufacturer.

Re: Envisioning a Simplified Intel Architecture

#50

Post by karmakaze »

I can certainly see how this is beneficial. At the same time it seems like it's a local optimum, to be eclipsed by other architectures. How much software really depends on 64-bit x86 architecture? And for how long?

A large amount of server software can be reasonably ported to a new architecture. New platforms can adopt new architectures (phone/tablet, AR/VR). General purpose software like a web browser abstracts hardware, as does very popular software (as Facebook had, and WeChat does).

Apple hasn't been tied to architectures and transitioned a number of times, always optimizing the whole rather than optimizing intermediate/stationary fixed points. If Intel is to make it to the next phase, it needs more than incremental improvements to compete. I hope that there's a path/future for AMD and Intel to evolve x86 and thrive but it won't be a given or easy.

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