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DOS specifications ("standards") (Developers)

posted by awik, 19.11.2020, 15:03

> Another topic for documentatition is the other stuff from Japheth's forge -
> the interface for JLM pluggins with his JEMM386 (they have .DLL extension)
> (however on the user level is sufficient to know the syntax
> DEVICE=JLOAD.EXE SOMETHNG.DLL)
That is interesting, because I am in a very preliminary phase of implementing a DOS multitasker inspired by the Win3/9x VMM+VxD layer. VMM is the kernel mode component of Windows 386 Enhanced mode, and incidentally implements DPMI (KRNL386 is in fact a DPMI application!), and VxDs (Virtual x Device; often with a *.386 extension) are loadable kernel modules. That sounds very analogous to JLMs.

It is feasible, though scarcely easy, to build an environment allowing the use of pre-existent drivers/modules from other systems. The "WDM" driver format used in Windows 98/Me proves that it is possible to support NT-style drivers. In the Linux world, there is "NDISWrapper", which allows Windows NDIS network drivers to be used for Linux. Soberly, that is more useful than supporting VxDs, although I much prefer the latter.

As deduced from beta releases of Chicago (Win95+DOS7), Microsoft was going to implement a "DOS=Enhanced" setting in CONFIG.SYS. This would cause DOS to load the VMM+VxD-layer. In this beta release the latter was contained in the file "DOS386.EXE" (which was WIN386.EXE in Win3.x, and VMM32.VXD in the commercial release of Win95). MS thought better of it -- probably due to DOS-negativity in the computer trade press.

I am rambling here, but maybe JEMM386 could be turned into a DOS386.EXE and FreeDOS could implement a "DOS=Enhanced" feature? DOS386 could load 32-bit kernel modules specified in a SYSTEM.INI file. These modules could implement hardware drivers, disk caches, etc. Then, maybe a basic KRNL386.EXE DPMI GUI application could be made to run on top of it? KRNL386 could in turn load a KERNEL32.DLL, which might perhaps be based on the pre-existent WINE implementation of the Win32 API. Alternatively, the system could make use of DLLs from modern Windows, because these are ubiquitous even though not freely available. In fact, the HX DOS extender already supports the use of Windows DLLs.

-Albert.

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