>> 1. Would like to ask how much memory does FreeDOS support, e.g. 4 GiB?
> Yes you'll be limited to a maximum of 4GB if you have 4GB or more. In
> practice this maximum could be anywhere between 2GB and 4GB (usually
> 3.3GB or 3.5GB) due to PCI chipset device mapping into the top of memory.

On older or "uncomplicated" mainboards, PCI should not take that many
addresses.   And yes, no one ever vioced any "serious" interest about
more than 4-GB of memory, so Japheth and I never pursued it in HIMEMX
or XMGR.   Can be done, but it requires "strong" agreement on all the
conventions used for the two drivers to access over 4-GB of XMS.

>> 2. Does it faces 640 KiB limitation as MS-DOS, e.g. Do I have to "load
>> high" drivers to save on conventional memory?
> yes. To access beyond 640KB load a driver (XMGR, HIMEMX, whatever) to
> access extended memory (XMS).

In fact, one needs an XMS driver (XMGR, HIMEMX, MS-DOS HIMEM, etc.) and
an "upper-memory provider" driver (JEMM386, MS-DOS EMM386, etc.).   The
"combined" JEMMEX can also be used.   If one uses only "real mode", the
UMBPCI driver can enable "Shadow RAM" (BIOS usage) as upper-memory, and
XMGR can then "provide" that memory to DOS.   No need for "EMM" drivers
in that case, but note that UMBPCI may not run with all newer chipsets.

The main point is that an XMS driver by-itself does NOT "provide" upper
memory to the DOS system.   This is done by the "EMM" driver, or by the
specific UMBPCI/XMGR combination.   [If XMGR does not find "Shadow RAM"
enabled by UMBPCI, it works the same as HIMEMX/HIMEM and "waits" for an
"EMM" driver to enable conventional upper-memory].

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