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Dave Yeo:

--- Quote from: Neil Waldhauer on January 25, 2024, 03:28:27 pm ---Can you be clearer about "incredibly slow"? We are running 1990s programs on 2020s hardware. How slow could it be?

--- End quote ---

With a decent JIT compiler, it could be almost as fast as native speed once a program is running, depending on the program.

Dave Yeo:

--- Quote from: Lars on January 25, 2024, 01:41:51 pm ---An X86 CPU can be emulated so that it will run OS/2. But OS/2 exploits almost all HW features of that chip, in contrast to DOS and Windows-16 bit (DOS only runs in real mode and therefore all "protected mode only" instructions are irrelevant, it also only supports 16-bit segments/operand and address sizes). And that will make the emulation incredibly slow.

--- End quote ---

Lots of DOS programs run in 32 bit protected mode, from using DOS extenders such as DOSGW (sp?) to Win 3.x and even Win9x. Even in 16 bit mode, those prefixes for 32 bit are available.
Reading up on it a bit, there's otvdm, based on winevdm, for running 16 bit software on 64 bit Windows, which due to design decisions (64 bit handles) does not run 16 bit and even 32 bit needs WOW. It uses the X86 emulator from Mame IIRC and works well.
There's also DosBox-X which is actually capable of running Windows XP as well as Win2K, which runs OS/2 1.x binaries mostly fine. Graphical programs need the Presentation Manager kit.
These emulators could be extended to support Ring 2 etc. It also raises the question about if OS/2 is running Protect Only, does it need as much CPU support.
Anyways, it will be a while before the new architecture takes over and who knows what AMD will do. I note that AMD brought back segments on the 2nd release under 64 bit to make virtulizers work better.


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