DOS ain't dead - DOS for 64 bits?

libz

17.10.2025, 23:37

DOS for 64 bits? (Users)

Hi all,

Maybe because I'm older now, I realize that focus is important. As is a distraction-free setup, as is speed of execution, as is simplicity.

DOS has all of this.
But everything I read about DOS is about the past.
16bit, 32bit, little RAM...

I don't know how to program in C or assembly, so I cannot help.
But could help in testing or in propaganda.

Would there be space for a DOS (like) for the present and for the future, that could use all the 64bit CPU, GBs (or even TBs) of RAM, with direct access to the hardware, that could beat all Windows and Linux in speed, simplicity and focus for the user?

kerravon

Ligao, Free World North,
18.10.2025, 10:34

@ libz

DOS for 64 bits?

Post reply

> Hi all,
>
> Maybe because I'm older now, I realize that focus is important. As is a
> distraction-free setup, as is speed of execution, as is simplicity.
>
> DOS has all of this.
> But everything I read about DOS is about the past.
> 16bit, 32bit, little RAM...
>
> I don't know how to program in C or assembly, so I cannot help.
> But could help in testing or in propaganda.
>
> Would there be space for a DOS (like) for the present and for the future,
> that could use all the 64bit CPU, GBs (or even TBs) of RAM, with direct
> access to the hardware, that could beat all Windows and Linux in speed,
> simplicity and focus for the user?

I believe UCX64 has all of that.

Available from https://pdos.org

Why do you want to directly access the hardware instead of doing
a UEFI call though? MSDOS did the same thing - a BIOS call.

Regardless, you can do either - even as an application.

But - like with MSDOS - you're officially supposed to do an INT 21H
call to access MSDOS services - but in UCX64 the INT 21H has been
replaced by a callback function instead. It probably could be done
via INT 21H though - if that served some purpose.

BFN. Paul.

kerravon Ligao, Free World North, 18.10.2025, 10:38 @ kerravon	DOS for 64 bits? Post reply
	Also, technically you don't even need to use UCX64. Just write UEFI shell programs. The advantage of UCX64 is that it allows you to run (certain) Win64 executables. But within that - if you want to access the hardware - go right ahead.

kerravon

Ligao, Free World North,
18.10.2025, 11:03

@ kerravon

DOS for 64 bits?

Post reply

> Also, technically you don't even need to use UCX64.
>
> Just write UEFI shell programs.
>
> The advantage of UCX64 is that it allows you to run (certain) Win64
> executables.

Also note that UCX64 comes with PDPCLIB, which contains
everything you need to write UEFI shell programs, if you
wish to go that route.

Or you can run those same tools on Linux or Mac - x64 or ARM64.
Or Win32 or Linux32 - ARM or x86.

I'm currently missing 32-bit MacOS support.

I have Motorola 68000 support, but it's not good enough to
produce x64 code - if you wanted to do that for fun. Same
applies to ARM32. ie you can't target x64 from ARM32 - I
don't have the required 64-bit support. But I may be able
to twist some arms to stop this requirement for 64-bit values
in the first place.

libz

22.10.2025, 22:00

@ kerravon

DOS for 64 bits?

Post reply

Hello kerravon,

Yes, I've been at https://www.pdos.org/ before.
I've read all of it, including some other texts by you and we have some common thoughts in several themes.

But I'm not a system programmer and I'm not at a level of knowledge that I can take what I read at the website and conclude that pdos is a DOS like system where I could run x86_64 applications.
I didn't get that idea before, and I hardly get it now.
The programming I do is about business data and associated areas. No C, or assembly.

The most relevant section for this seems to be 'University Challenge x64'
So, what I miss is a tutorial where it could be shown step by step what to do to have pdos booting in a x86_64 hardware (and in other ones as well).
I'm unaware of what could be done using EFI. It seems that you've programmed pdos to run as a UEFI module, is that correct?
Can pdos run 64 bit programs and use GBs of RAM and big files?
Can pdos run all ancient MSDOS programs, like Turbo Pascal, Norton Commander, etc?

Some howtos and some videos would be of great help for me and for others like me that don't have your level of expertise in the subject.
I know, I know, it's a lot of work that I'm asking.

Thank you,
All the best.

kerravon

Ligao, Free World North,
23.10.2025, 04:16

@ libz

DOS for 64 bits?

Post reply

> The most relevant section for this seems to be 'University Challenge x64'
> So, what I miss is a tutorial where it could be shown step by step what to
> do to have pdos booting in a x86_64 hardware (and in other ones as well).
> I'm unaware of what could be done using EFI. It seems that you've
> programmed pdos to run as a UEFI module, is that correct?

Yes - I'm not sure "module" is the correct term, but I don't
know what the correct term is.

Modern x64 computers all use UEFI. It's very difficult to find
a BIOS now.

Do you want to run on real hardware or under Virtualbox etc?

I provide a VHD. You can use that directly in Virtualbox or
you can burn it to USB stick using Win32 Disk Imager. If
doing the latter I think you need to rename it to .img.

> Can pdos run 64 bit programs and use GBs of RAM and big files?

Theoretically it can be rebuilt to do that.

Currently it is mimicking Microsoft Windows and Microsoft
Visual C, which uses 32-bit long still - and that is what C90
gives.

So for now, no big files.

For big memory - a different issue - previously I was using
cc64 and that needed to be restricted to the lower 2 GiB.
I am now using mcc, but haven't fully migrated, so the
restriction remains.

> Can pdos run all ancient MSDOS programs, like Turbo Pascal, Norton
> Commander, etc?

It can't run any of them. You need to recompile for the x64
platform.

What did you expect when you asked for DOS to be 64-bit?

Genuine question - I'm interested in your opinion on the
very definition of "DOS". It's philosophy to me.

It will run some existing genuine Win64 x64 programs though
(mainly ones that I built).

But that is also a philosophical question - is the Win64 command
prompt "64-bit DOS" too?

> Some howtos and some videos would be of great help for me and for others
> like me that don't have your level of expertise in the subject.
> I know, I know, it's a lot of work that I'm asking.

I can guide you through it (in this forum, in text) if you start by
telling me where you want to run it. You can make a video at
the end of that process if you wish. Or a HOWTO. You offered
to do something non-programming for the "64-bit DOS", right?

kerravon Ligao, Free World North, 23.10.2025, 04:29 @ kerravon	DOS for 64 bits? Post reply
	> you can burn it to USB stick using Win32 Disk Imager. If > doing the latter I think you need to rename it to .img. I think I remember now - the trick is to choose "all files", otherwise "vhd" isn't visible. It's Bochs on Android that may require you to rename the vhd to img.

kerravon

Ligao, Free World North,
23.10.2025, 05:59

@ kerravon

DOS for 64 bits?

Post reply

> What did you expect when you asked for DOS to be 64-bit?

Just a bit more on the philosophy.

The traditional MSDOS interface was defined in assembler,
with calls to INT 21H, that included some calls with parameters
given in segment registers.

It's not possible to reproduce that exactly in x64. You can't
manipulate segment registers like that, and it defeats the
purpose to use the exact same 16-bit registers - you need
to upgrade to 64-bit registers.

So. Existing assembler source needs to change.

And most people - even on MSDOS - were writing in C, not
assembler, anyway.

And if existing assembler source needs to change - then what
is "acceptable" to get the "DOS" label?

Also - is there a particular reason to want that exact label?
What's the underlying objective?

And if the original source is written in C - particularly if it
conforms to the C90 standard - then yes, that "DOS program"
will work on 64-bit "DOS" too.

It will also work on any machine that is called "definitely not DOS".

So at some point, I get lost.

Being lost in terminology doesn't prevent me from getting
software to run though.