[comp.sys.ibm.pc.misc] emm40.sys - expanded memory

wg@cbnewsm.att.com (Bill Gieske) (08/16/90)

I have a 2MB 286 with a NEAT chipset, which provides expanded memory (4.0
level).  For some reason, the NEAT chipset will not allow me to split the
second meg as half expanded and half extended - it's either all one or the
other.  In trying all extended, and using emm40.sys from PC Magazine or
from Simtel's BB, I noted that emm40.sys loads within the 640K area.  This
appears to be the only way it will load.  Do I have this correct?  Is there
more to this than I've described?  Any way to optimize its memory use?
Replies please to:

	wg%alux2@research.att.com or att!alux2!wg

Thanks!

Bill Gieske
AT&T

RFM@psuvm.psu.edu (08/17/90)

Extended memory is different from expanded.... You can designate some
expanded memory to be treated as expanded, but you cannot go the
other way--expanded to extended. Wish you could.... Bob M.

levericw@clutx.clarkson.edu (Allanon, ,,3152655399) (08/17/90)

From article <90228.143145RFM@psuvm.psu.edu>, by <RFM@psuvm.psu.edu>:
> Extended memory is different from expanded.... You can designate some
> expanded memory to be treated as expanded, but you cannot go the
> other way--expanded to extended. Wish you could.... Bob M.

I'm confused here, is not all memory above 1Mb exTENDed until you
install an EMM device driver?  If so why would you want to go exPANDed
to exTENDed, just make the driver allocate a smaller number of pages.

Walden

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darcy@druid.uucp (D'Arcy J.M. Cain) (08/18/90)

In article <1990Aug16.202610.28641@sun.soe.clarkson.edu> levericw@clutx.clarkson.edu writes:
>From article <90228.143145RFM@psuvm.psu.edu>, by <RFM@psuvm.psu.edu>:
>> Extended memory is different from expanded.... You can designate some
>> expanded memory to be treated as expanded, but you cannot go the
   ^^^^^^^^ <--- He means extended
>> other way--expanded to extended. Wish you could.... Bob M.
>
>I'm confused here, is not all memory above 1Mb exTENDed until you
>install an EMM device driver?  If so why would you want to go exPANDed
>to exTENDed, just make the driver allocate a smaller number of pages.
>

Sigh.

Why do people have to add unneccessary terms to the language.  OK, here
are the proper terms.

Extended memory -- memory | native memory | additional memory
Expanded memory -- Banked memory

Now think of the regular memory in an IBM-PC as "Partial memory."  Extended
memory is just add-on memory on systems with chips that can directly address
it.  The only thing "extended" about it is that IBM and Microsoft think
that the world ends at 1 megabyte.

Lotus, Intel and Microsoft invented a banked memory scheme (Hence LIM) which
was designed to get around the DOS 1 megabyte limit.  Now LIM memory was
designed to work in systems that could not address more than 1 megabyte.
Therefore, the only way to get more memory was to use a banked memory
scheme.  The physical memory is banked into an area of memory that can
be addressed directly by the 8088 or 8086 chip.

So the important point here is that the memory known as expanded is not
necessarily "above" the 1 megabyte line.  It may be within it.  The only
time it is above is when extended memory is used to emulate banked memory.
The EMS driver has the processor move a block from above 1 megabyte into
the space below so that DOS can see it.  Thus extended can emulate expanded
but if you have an expanded memory board (especially in a PC ot XT) you can
not use it as extended or native memory.  You must bank it in to native
memory to use it.

So why did Lotus/Intel/Microsoft invent the new names.  Are they trying
to make people think that they invented something new?  I can see them
siting around a table cackling over the fact that "extended" sounds so
much like "expanded" that they will be able to confuse the maximum number
of users with that terminology.

-- 
D'Arcy J.M. Cain (darcy@druid)     |
D'Arcy Cain Consulting             |   MS-DOS:  The Andrew Dice Clay
West Hill, Ontario, Canada         |   of operating systems.
+ 416 281 6094                     |

einari@rhi.hi.is (Einar Indridason) (08/19/90)

In article <1990Aug18.131250.18988@druid.uucp> darcy@druid.uucp (D'Arcy J.M. Cain) writes:
>In article <1990Aug16.202610.28641@sun.soe.clarkson.edu> levericw@clutx.clarkson.edu writes:
>>From article <90228.143145RFM@psuvm.psu.edu>, by <RFM@psuvm.psu.edu>:
>>> Extended memory is different from expanded.... You can designate some
>>> expanded memory to be treated as expanded, but you cannot go the
>   ^^^^^^^^ <--- He means extended

What about some mnemonics?

exTended is memory on Top of the 1MBYTE limit.  Notice the 'T'
                      ^^^

exPanded is memory that is Paged in.  Notice the 'P'
                           ^^^^^
--
I just learned a new curse: "You #$@! son of SCROLLBAR!"

Internet:       einari@rhi.hi.is   | 'Just give me my command line and throw
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liberato@drivax.UUCP (Jimmy Liberato) (08/20/90)

darcy@druid.uucp (D'Arcy J.M. Cain) writes:

>So why did Lotus/Intel/Microsoft invent the new names.  Are they trying
>to make people think that they invented something new?  I can see them
>siting around a table cackling over the fact that "extended" sounds so
>much like "expanded" that they will be able to confuse the maximum number
>of users with that terminology.

Yes, and add the fact that IBM likes to call extended memory expansion
memory (not to be confused with expanded memory). 

--
Jimmy Liberato   liberat@dri.com
                 ...uunet!drivax!liberato