On Tue, Jun 28, 2016 at 12:56 PM, Abe Mishler <a...@mishlerlabs.com> wrote:
> It's apparent that a well written book might help me come up
> to speed on all of these memory modes and managers.
I'm not an expert, but the simple answer is you don't need all of
them. Pure XMS (and optional DPMI) should suffice for most uses. Don't
overcomplicate it. Don't worry about every feature under the sun
unless an app you want to run direly needs it (unlikely). EMS is quite
old and rare, and even without EMM386, the amount of conventional
memory free should be "good enough" for most existing programs, so you
probably don't need UMBs at all. (But see UMBPCI. Or EMS Magic, which
reuses conventional memory, which is sometimes better for
compatibility.) Besides, you can "JEMM386 LOAD" (and "UNLOAD") later
if you (temporarily) need EMS for something (but not for UMBs).
Somebody, when preparing FD 1.1, was perhaps overzealous for features
when trying to support JEMMEX. But, for the record, VBox is not
necessarily bug-free or a primary target (remember that DOS is meant
for actual native booting, or at least was before UEFI). So yes,
presumably EMM386 (et al.) work better on "real" native hardware than
emulators. That can't be avoided, but perhaps it's not wise to
recommend (or even include) overcomplicated JEMMEX config lines in
future FD versions. (This has been discussed before, so you're not the
first one to notice this hanging VBox + JEMMEX behavior.)
P.S. Emulators are still (usually) run on top of advanced host OSes.
So I'm not sure certain low-level DOS things are directly useful there
(software cache, screen saver, ultra DMA). So I wouldn't worry about
> My interest is in programming anyways (I'm new to DOS but not programming).
> Any suggestions?
The officially recommended compilers / languages are C (OpenWatcom)
and assembler (NASM). But the DJGPP tree is quite nice too (and
includes barely-related offshoots like Free Pascal, FreeBASIC, and
more). None of these need EMS or UMBs.
So it's unlikely you'll be interested in EMS at all. Stick to real
mode (640 kb) or DPMI (2 GB).
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