Hi, Bart told us about FAT32 and 186/386 optimization versus kernel size
in RAM, especially in HMA:
HMA: HEX DEC
8086 80186 80386 8086 80186 80386
FAT16 995c 9694 94c5 39260 38548 38085
FAT32 a7cb a4ed a24a 42955 42221 41546
i.e. FAT32 adds ~3.5-3.7K; 386 optimizes out ~1.2-1.4K
For more details, check the thread about FreeDOS beta 9 rc 5 on the
freedos-devel list.
Now my question (which Bart asked me to ask in public)...:
I have the impression that only kernel devices and all kinds of
"public" (more or less documented) data structures for which a
normal DOS program can find a pointer easy are still inside the
first 1 MB of RAM (low DOS RAM or UMBs), plus some wrappers to
make sure that A20 is on before the rest of the kernel / data,
which got moved to HMA, is accessed.
So...: What parts of DOS are actually still in low DOS RAM and
are there chances for serious optimization there? Question 2:
Which parts are in low DOS RAM instead of in UMB and why?
I assume that even if you set your A20 to "glued to on" then still
some programs would be confused by FFFF:???? style pointers so you
probably should not attempt to move "everything" of DOS into HMA,
so THAT kind of optimization would not be recommended.
Eric
PS: Konstantin reports that MS HIMEM "allocates" (well, it provides
it itself, so it just does not give all of it to DOS) a chunk of HMA
memory for itself to put about 1/2 of its resident size there. One
example of "funky methods to squeeze out more free RAM", but I myself
would prefer using UMBs to get more low DOS RAM free (which is no
really good option for HIMEM which you often load before UMBs exist).
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