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DOS for 64 bits? (Users)

posted by libz, 07.11.2025, 16:47

> > I have several low powered thin computers that are able to run both BIOS
> > and UEFI.
> > UEFI is the future so I'm fine with using it from the time being, and
> can
> > use one of them to run PDOS.
> > So, I'm interested in running in real hardware, although can test in a
> > virtual host before, for convenience.
>
> Ok.
>
> > > > 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.
>
> > Ok.
> > I'll have some work to do, then!
>
> The chances of any of those things being C90-compliant are
> close to zero, so it's not just a recompile that is required.
 So, the usefulness of PDOS for an end-user is very limited.

> > I've read that 4DOS is public domain.
>
> https://en.wikipedia.org/wiki/4DOS
>
> It's copyrighted (modified MIT), not public domain, according
> to that.
 I took the idea that 4DOS was public domain from https://web.crouze.com/the-return-of-4dos/ where it is said that "the old 4DOS is also still very much alive and kicking! The latest releases are in the public domain now, and have constantly been in development.".



> I make some limited exceptions as a means to an end, and
> the end is to have completely public domain software so
> that I can fix anything I want, and it isn't owned by someone
> else who wrote the buggy software in the first place.
 I understand that.


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


> How do you actually know that? First of all, the MSDOS command
> prompt (command.com) doesn't directly access the hardware - it
> does calls to the MSDOS OS proper (msdos.sys). And even that
> doesn't access the hardware directly, it does BIOS calls.
>
> (As far as I am aware, anyway - now that we have the MSDOS 4.0
> source code we can find out for sure - but that in itself defeats
> the whole purpose of finding out in the first place - if it's not
> possible to detect as an end user, and you have to spend an
> awful lot of effort to prove that - what difference does it make?).
>
> You could argue that MSDOS apps can CHOOSE to access the
> hardware directly if they want - well - that's largely because the
> processor itself doesn't have a way of stopping you - and that's
> not necessarily a good thing. Can you tell me why you think that
> would be a good thing? Getting some sort of hardware demo
> started quickly - even if MSDOS crashes a lot while attempting
> to demo that?
>
> If that is the "target market" - then there are still alternatives -
> like creating an extension to the MSDOS API that allows you to
> write "directly" to an I/O port.
 Sorry, I just meant the least possible indirections.
Have no knowledge to discuss these technical details.


> Or what about if the Windows 11 command prompt operated in
> ring 0 - would you be happy then? Do you need it to bypass
> virtual memory too? The PDOS "Windows clones" don't use
> virtual memory - so that could be what you're after - bypass
> the complication of virtual memory.
 There are videos in Youtube explaining how undocumented Intel cpu instructions allow someone to run in ring 0.


> That's what I was after, basically/sort of.
>
> > > > 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?
 If PDOS can be useful to me, I'll do it, although at a slow pace.



> > Yes, I'll do it, at a very slow pace, but I'm interested.
> > So, to begin with, copy the ucx64.zip (unzipped) or the pdos.zip to the
> > UEFI partition and boot from there, right?
>
> Not really.
>
> You mentioned you were interested in running on a virtual host
> before putting it on a real computer.
>
> So start with that. Which virtual host are you interested in using?
> I support both Oracle Virtualbox and qemu.
>
> In both cases, you just point it to the VHD (hard disk image)
> within the zip file.
 I'd prefer qemu, as have not Virtualbox installed and would prefer not to waste space on it.


> UCX64 you need to go to the extra effort of enabling UEFI (a
> checkbox in Virtualbox, but qemu is a bit more complicated).
>
> Note that on real hardware, you could indeed unzip ucx64.vhd
> (not .zip) onto a "UEFI partitition". But pdos.vhd needs to be
> burned as an image - you can't just unzip it.
>
> > Are the two ucx64 and pdos systems at the same level of development, or
> > which one is more advanced for me to try?
>
> The BIOS-based PDOS/386 is the most advanced.
 Alright.

>
> But the future is expected to be UCX64 for a different reason -
> the public domain C compiler (mcc) now available.
 Great.


> > Given what you said above regarding the limitations of the 64 bit
> version,
> > can it be considered to be equally constrained at the 32 bit word and
> 2GB
> > of RAM?
>
> Yes, both are equally constrained in RAM currently.
>
> But one of the reasons I am in this "DOS Ain't Dead" forum in the first
> place is because I believe the software industry went into a dead end,
> and I want to start again with 640k of RAM and negotiate why we need
> an increase from that.
>
> If 2 GB is a constraint for you, you might want to rethink your life
> choices. :-)
 For a focused standalone desktop computer, yes, I agree.
But it could be an alternative system for 64 bits to be able to process the very big amounts of data that we process nowadays and that were not available at the time of the legendary MS-DOS.


> Here is something someone else wrote:
>
> https://www.quora.com/Why-did-you-leave-a-job-as-a-software-engineer/answer/Jeff-Sturm-2
>
> His "solution" was to leave the industry.
> My "solution" involves a return to MSDOS - or something similar.
 But to a mighty PDOS!

>
> EDIT: I forgot to mention - I completely rewrote pdos.org from scratch to
> explain what the current situation is with PDOS. Previously it was created
> in an adhoc manner as breakthroughs happened in a fairly random fashion.
 I had seen it, thanks.

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