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Re MS-DOS7 bug, Patch done! available soon :=) (Miscellaneous)

posted by cm(R) Homepage E-mail, Düsseldorf, Germany, 24.11.2009, 23:11

> The list is built properly including info for those TSRs which
> were loaded by Wrapper.sys (with my hack loaded of course).

Neat!

> As for the memory eaten up by my solution, well it's only 368 bytes (and
> can be loaded in UMBs, if available, by DEVICEHIGH). Note it is only
> /once/ 368 bytes however many TSRs are subsequently loaded using
> Wrapper.sys or similar.

I understood that. But it still wastes memory.

> The memory is not needed after driver init is
> finished - so it /could/ be unlinked from the device driver chain and made
> available for allocation to DOS programs, by manipulating the MCB chain.
> But it is so small a patch of memory lost in the middle of DOS drivers
> area that I don't think the "return on investment" of a specific unloader
> is worth it

Why not manipulate MCBs during the installation and allocate the table in another memory block (at the top of low memory, or at the top of a UMB)? This is very simple for UMB installation because DOS doesn't seem to be allocating all UMBs right away. However, DOS likely allocates all low memory to your driver if it's loaded there, so you have to resize this MCB yourself.

Besides, a small environment sure fits in this space.

> (when my little thing is released for "beta" testing, you are
> welcome to write one however ;)

Write it yourself. The solution mentioned by you is simple, you just have to find your sub-MCB and then split or resize the system MCB that contains your driver. This could be integrated as executable into your program, so that the file would be a dual .COM/.SYS or .EXE/.SYS file.

> > How does your version check identify
> > the offending MS-DOS versions?
>
> First, let it be remarked that since this program is only ever of use on
> Win-DOS 7 or 8, and advertised as such, a user /should not/ try to load it
> under an offending DOS !

Because it might crash these perfectly fine DOS versions if it misdetects them as MS-DOS ;-)

> However I'll do my best effort to identify genuine MS-DOS from Windows
> 9x/ME and I hope for you guys to check it works against those non MS DOSes

I'll certainly try it.

> > what if MS-DOS 9.50 removed support for, say, UMBs?
>
> DOS ver 9 is the OS2 'compatibilty box' IIRC.

Nope, that's "DOS versions" 10 and 20.

> It is not likely there will
> ever be an MS-DOS 9.50 (nor any MS-DOS ver over 8, for that matter)

Indeed. But the MS people probably didn't know that back when they released MS-DOS 5.

---
l

 

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