New DOS DPMI project?

Aitor posted this note to the FreeDOS mailing list about a new DOS DPMI project:


I have thought that you might find it useful to have a look at this page: http://www.wuschel.demon.co.uk/

they are developing a DOS-Extender that supports a lot of technologies: VCPI, DPMI and XMS.

Along the same lines, I have been doing some 'research' about my 'favorite' obsession, the multitasking environments for DOS.

Unfortunately, DPMI specifications say nothing about multitasking. I have been talking to the author of CWSDPMI, he says he's close to release the r5 version, and that it is about to give the project for finished, so it won't go beyond. I was asking him how did he feel about multitasking.

Excerpt from our conversation:

> Does the DPMI specification say anything about multitasking?

No. DPMI provides DOS services - and DOS isn't multi-tasking. It assumes if there is a multi-tasking layer it is at a higher level - probably multiple virtual machines with an operating system providing the tasking.

> Would it be possible to build up a DPMI server with preemtive
> multitasking capabilities? Changing preemtive for cooperative?

Various versions of Windows have done this. I've also run CWSDPMI under Deskview (multitasking) a long time ago.

To directly put it into the DPMI provider would be a lot of work.

> Is there something planned about it?

I have no plans to make significant changes to CWSDPMI. I can't even find the time to debug the 1 reported bug which prevents me from releasing r5.

> Or, do you know of a free multitasker for DOS environments, that would
> allow (cooperative, or better, preemtive) multitasking and running 32-
> bits DPMI applications?

I have heard that the DRDOS 7.3 supports both multitasking and DPMI.

I have asked as well to the WDOSX maker, but I believe that he might not reply unless I get into the mailing list. I have seen that there are some programs in Simtel, but I don't know if they are free or have sources.

Please, don't think that I am trying to discourage you. For the contrary, I am trying to provide sources of information for your project, or alternatively, avoid your wasting your time in the case you consider that there is already a free program that does what you meant. I feel that this might be a very important project.

As we have seen, you will know that multitasking for DOS is difficult stuff, maybe involving a virtual machine manager (perhaps 32-bit program) and possibly 'outside' the DPMI server. If you wish to continue, I would like to support you as much as I can, although it will be (at least in the beggining) with sources of information in the net, as I have taken over too many projects lately.

-Aitor


David Lloyd responds:

> Unfortunately, DPMI specifications say nothing about multitasking.

Not true.. the 1.0 specification has some very relevant functions for multitasking. I am hoping to implement FREMM386 to be able to support multitasking. It won't multitask itself; you'll need to add a module but I will put the support there for sure. The multitasking must be done by the DPMI service provider, maybe that's what he means.

> Please, don't think that I am trying to discourage you. For the
> contrary, I am trying to provide sources of information for your
> project, or alternatively, avoid your wasting your time in the case you
> consider that there is already a free program that does what you meant.
> I feel that this might be a very important project.

Nothing does what I want for free. The only thing that comes close is QEMM386+Desqview, and not only is that not free, but you can't even get Desqview anymore!

> As we have seen, you will know that multitasking for DOS is difficult
> stuff, maybe involving a virtual machine manager (perhaps 32-bit
> program) and possibly 'outside' the DPMI server. If you wish to
> continue, I would like to support you as much as I can, although it will
> be (at least in the beggining) with sources of information in the net,
> as I have taken over too many projects lately.

So far it's going well. It will be lots of work but I have a lot of information, and I am confident that I can do it. Once I get my website up (hopefully next week) I will have more information on what my goals are, and how I intend to implement the server. Look for it next week at: http://www.freemm.org

I will post more info when it is available.