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. ______ Dennis https://plus.google.com/u/0/105128793974319004519 ------------------------------------------------------------------------------ This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
