On Mon, Jun 30, 2014 at 1:30 PM, Zbigniew <zbigniew2...@gmail.com> wrote:
> 2014-06-30 19:19 GMT+02:00, Rugxulo <rugx...@gmail.com>:
>> IIRC, 4DOS can swap out (since it's quite large) to conserve
>> conventional memory. You may have to change that setting (SWAPPING ??
>> I forget ...). I don't think it's something inherently wrong with
>> 4DOS, but who knows.
> But I already wrote, that when using JEMMEX and 4DOS I had more memory
> available (both conventional & upper), than using XMGR + FREECOM? And
> - despite of this - that only in latter case I could switch to shell
> from TC's IDE?

I've encountered that in other contexts.

4DOS works essentially the same way a COMMAND.COM.  There is a
resident portion and a transient portion.  When you load the shell,
the resident portion is relocated to the top of available memory.
When you run a program from the shell, the transient portion is
overwritten by your program to give it more conventional memory.  When
you exit the program, the transient portion is reloaded, using the
SHELL= line to specify what to reload from and where to find it.  (If
you use a stock system with COMMAND.COM, you don't need the SHELL=
line, because DOS will reload from \COMMAND.COM on your boot drive.)

The transient portion of 4DOS is much larger than than that of
COMMAND.COM.  4DOS will let you swap most of itself EMS, XMS, or disk,
depending on what you specified in the SWAPPING config, to leave more
room in conventional RAM.

The problem is what happens when you shell to DOS from within an
application.  You are attempting to load COMMAND.COM or 4DOS in the
conventional memory left over by the application you shelled from.  If
your application takes enough conventional memory, 4DOS will fail to
load because there isn't enough room left for its transient portion,
but COMMAND.COM will work because it will fit.

I tend to invoke such applications from a batch file that sets SHELL
to point to COMMAND.COM instead of 4DOS, and invoke the app by
"command /c app" to start it from COMMAND.COM.

> Z.

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