VOGONS


First post, by sliderider

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https://www.tomshardware.com/news/intel-ponde … 6s-architecture

Intel wants to discontinue legacy support in future x86 CPU's. It says they are considering pruning features dating all the way back to the 8086/8088 era, so I would imagine that any emulator that calls on these features at the hardware level, will no longer be able to in future x86 CPU's, and would need to use software emulation of these features, or am I assessing this incorrectly?

Reply 1 of 7, by dr_st

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I don't think DOSBox calls any of these features at the hardware level, does it? SW emulation of x86 features is exactly what it does (hence it has builds for x64 CPUs and for ARM CPUs as well).

Maybe some specialty features / custom builds offer passthrough to hardware in a non-portable way? That could be jeopardized if HW support goes away.

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Reply 2 of 7, by sliderider

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dr_st wrote on 2023-05-21, 07:43:

I don't think DOSBox calls any of these features at the hardware level, does it? SW emulation of x86 features is exactly what it does (hence it has builds for x64 CPUs and for ARM CPUs as well).

Maybe some specialty features / custom builds offer passthrough to hardware in a non-portable way? That could be jeopardized if HW support goes away.

I don't know anything about how DOSBox works, I just thought I'd mention it in case it did have any hardware dependencies.

Reply 3 of 7, by Zup

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I guess it won't affect DOSBox at all.

It seems that they will drop 16 bits instructions, but DOSBox does not have 16 bits instructions in it's code. The thing is that DOSBox uses 32 or 64 bits instructions to actually emulate the behaviour of the CPU (opposed as virtual machines like Virtualbox or VMWare, where the CPU is actually executing those instructions).

It seems confusing... i will reword it...
- DOSBox (or any emulator) "translates" your game instructions to your CPU instructions. That makes possible to execute it in any CPU (that is fast enough), so you can execute an old 8086 game in an Raspberry PI (that has an ARM CPU that is not based in x86 architecture).
- Virtual machines like VMWare feeds your game instructions directly to your CPU, so they need a CPU based on same architecture (with virtualization hardware) to actually run your code. I mean that, if you want to run x86 code you will need an x86 CPU (AMD Ryzen, Intel i5)... you won't be able to run your 80286 code on a virtual machine based on an M1 machine (unless your virtual machine provides some kind of emulation).

So I don't guess DOSBox will be affected (worst case: it will need to be compiled for new processors... but the source code won't be changed). On the other hand, Virtualbox and VMWare will need to recode a x86 emulator if they want to support MS-DOS guests.

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Reply 4 of 7, by jmarsh

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IIRC there are some 16-bit addressing instructions generated by the x86_64 dynamic core but the PDF says they are unaffected.

Reply 5 of 7, by llm

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sliderider wrote on 2023-05-21, 07:06:

or am I assessing this incorrectly?

dosbox does not rely on any hardware features - its a full blown software-emulation of the old hardware, so recompiling of dosbox itself would be enough

Reply 6 of 7, by Jo22

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The dynarec core (dynamic recompiler) has some x86 dependencies, AFAIK.
But it's not exactly tied to the original 8086 instructions, maybe. More like i386, I assume.
Anyway, it's not going to break DOSBox. A small modification/recompile should get around this issue. That being said, I'm merely a user. 🤷‍♂️

Edit: Hm. Rings 1 & 2 are being removed in X86-S. 16-Bit Real-/Protected Mode and Segmentation support, too. - This may affect Wine/Wabi on modern Linux, too. Or recent OS/2 (ArcaOS), which can boot from UEFI.
Then the list goes on with 32-Bit Ring 0, V86, the old 8529 PIC, x87 FPU bits (CR0)..

Doesn't look nice. As I worried/warned for years, Intel finally began killing the roots of x86.
The forcefully removable of CSM (BIOS emulation) was the start. It needed Real-Mode the most. Then the decline of shipping VGA/VBE BIOS in recent graphics cards.
If things go on, hardware-assisted virtualization (AMD-V, Intel VT) will suffer from this, too.

Edit: On the other hand.. This is "just" a white paper.
Maybe intel is testing reactions of the IT? Some sort of provocation, to see if anybody cares?

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Reply 7 of 7, by leileilol

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It would sooner break dosemu instead.

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