On Thu, Jul 4, 2013 at 4:17 PM, Bertho Grandpied <y31415926...@yahoo.fr> wrote:
> On Thu, 4 Jul 2013 21:08:12 +0200 Tom Ehlert <t...@drivesnapshot.de> wrote :

>> where would you put it and why ?
> The "why" has been explained. In addition, under /some but not all/ BIOSes, 
> it seems the presence of a DOS MCB-covered zone under the 'video' area may 
> perturb conventional memory reporting by the API of int 15/E820. Not 
> confirmed. Want more ? OK, additionally, some (admittedly very rude, maybe 
> very old) DOS programs will neglect to check where the memory 'above' them 
> ends, and use any and all "BIOS int 12" mem without reservation. for that 
> reason the end of the 'transient program area' should as far as possible 
> coincide with the end of conventional (int 12) memory.

Placing the environment at the top of conventional memory is what
MS-DOS COMMAND.COM did, and FreeDOS tries to be DOS compatible.

I never had a problem because of it.  One thing I used to run on my
old PC XT clone under MS-DOS 3.3 and 5.0 was a freeware utility form
Chris (CED) Dunford.  It could map unused video memory in the segment
above 640K to DOS conventional memory.  With a CGA card you could get
96K of additional RAM.  With my Hercules card, I could get 64K. so I
booted to a system that had 704K of conventional memory.  COMMAND.COM
putting the master environment at the top of conventional memory did
not cause a problem.

While it might be nice to relocate the master environment block
elsewhere, like upper memory, it's hardly necessary.  People lived
without being able to do so for decades without problems.  I don't
ever recall hearing about the sort of problems you raise as
possibilities, and I'd call the chances of them happening rare enough
to not be worth worrying about.

If you insist on this behavior, feel free to submit a patch that adds it.

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