🚀 go-pugleaf

mcc@wlv.imsd.contel.com (Merton Campbell Crockett) writes:

>This will seem like a terribly naive question to many of you--it does to
>me; however, I would like to understand the difference between extended and
>expanded memory.

Extended memory is memory above 1 Mbyte that is directly accessable to an
80286/386/486 in 'protected mode'.  When theses chips first boot up they are
in 'real mode' which is completely compatible with the original 8088.  In real
mode there is 1 Mbyte of memory total, divided into 64K segments.  MS-DOS only
understands real mode, which is why it is limited to 1 Meg (640K because the
video buffer starts at 640K, and the addresses above that are used for ROMs).
In order to access extended memory, an extended memory driver must be used
to switches the chip into protected mode, retrieve the data requested, and
then swap back to real mode.  On 386 and 486 computers, it is possible for
software to map parts of extended memory into unused addresses above 640K.
Programs such as QEMM386 and 386 to the Max will let you load device driverss
and TSR programs into this remamped memory.

Expanded memory is memory which is access via a 64K window below 1 Meg.  In
order to access this memory, programs tell the expanded memory driver to swap
the desired 64K into the window, at which point the program can do what it
wants with it.  This memory can be available on any computer from an 8088 to
a 80486.

If you have a 386 or 486, I would suggest using extended ram with a memory
manager such as QEMM386.  QEMM will convert extended ram to expanded ram when
needed depending on what kind of memory programs ask for.
-- 
Jay Hofacker, sysop of the Audio/Visual Exchange, (606)254-1751 3/12/24 MNP 5
Mail: jayh@ms.uky.edu or uk02779@ukpr.uky.edu -- Yes, my signature is only 2 lin