Hi,
On Thu, Mar 15, 2012 at 3:39 PM, Jack <gykazequ...@earthlink.net> wrote:
>
> I have saved XMGR for "real mode" users who run UMBBCI first, followed
> by XMGR. In that case, XMGR is able to "read" UMBPCI's table of UMBs
> and can load there directly, which also uses 0 low-memory like JEMMEX.
> UMBPCI cannot "map" the B000h-B7FFh space ("black and white" graphics,
> that no one uses any more) into upper-memory. But DOS games players,
> and others who want real-mode speed (like me!), normally get over 128K
> upper-memory, which is O.K. for our needs. So, UMBPCI + XMGR is the
> only useful "old" configuration -- Most users should run JEMMEX alone.
Unless you need EMS, you don't truly need JEMMEX itself. Last I
checked, I don't think it would let you run XMS only unless you did
"NOEMS", and even that still left you in V86 mode. Granted, it should
be fine for "most" software, but it's not a perfect solution (not that
one probably exists anyways).
Nowadays, it does seem most DOS software is either real-mode or 32-bit
DPMI, though some XMS creeps in too. And CWSDPMI won't use 4 MB pages
if you're running EMM386, so that's a speed drop (but then probably
doesn't use those anyways unless you're making huge allocations as
there are other minor compatibility nits).
It all depends on what you're trying to do. Turbo C uses EMS (if
found) by default, and of course DJGPP uses DPMI (which uses whatever
it can find). Obviously there's no comparing the two in speed, but the
point is the same: different approaches to the same problem. Feel
free to benchmark them, but the results are unlikely to matter much
unless you do it a lot in succession.
> DOS also retains its single-sector directory handling, designed back in
> the early 1980s, when memory was EXPENSIVE and buffers were kept
> small.
Two of the biggest hurdles to using DOS software often seem to be
memory management and file system quirks. I know there are other minor
things too, but those are the ones that seem to come up a lot. But
with DPMI and FAT32, that's fairly moot, thankfully.
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