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S_BUCK@rzmain.rz.uni-ulm.de (Buck Martin) writes:

>First, the question about EMM386:
>What is the use of its L=xxxx switch? I know it's used to reserve a
>certain amount of extended memory, but why do I have to use this
>switch? When I have 3Mb of extended memory and want to use 1Mb of it
>as expanded memory, I write: EMM386 1024 RAM. Is it true, that in
>this case EMM386 takes the whole 3Mb of extended memory, changes 1 Mb
>to expanded memory and leaves the other 2Mb unused (and inaccessi-
>ble)? If so, what is the reason for this? If not, how does it really
>work?

I can't find any reference to the L option in the DOS 5.0 reference
manual.  The only options I see mentioned are RAM and NOEMS (plus the
obvious size).  When you say 1024 RAM, you are providing 1Mb of EMS
memory (minus any memory which gets mapped into the 640-1Mb area).
The rest is XMS (if you've loaded HIMEM).

>I'd also like to know, if there is any (shareware) expanded-memory-
>manager for the 386 that doesn't switch the CPU to virtual mode (if
>this is possible at all). If such an emulator exists, where can I get
>it from?

It's my understanding that it is possible (under particular chipsets
only) to map memory from >1Mb into the area 640-1Mb.  ie, provide UMBs
without going into V86 mode.  It would be then possible to emulate EMS
using XMS, although I don't believe this has been written (yet).  I
don't really see the point, though.

>My third question is about the DOS=HIGH feature when using HIMEM.SYS:
>Is there any possibility to prevent Mess-DOS from using the HMA if
>there is a DOS=HIGH statement in the CONFIG.SYS? As far as I know,
>DOS prescans the CONFIG.SYS before loading any drivers and searches
>for a DOS=HIGH statement. If the last DOS= statement is DOS=HIGH,
>then DOS reserves the HMA as soon as it becomes available (after
>loading HIMEM.SYS).
>Does anybody know, how to force DOS into low memory though there is a
>DOS=HIGH statement (it must be possible; I've seen 2 multi-configura-
>tion-programs doing this)?

You betcha.  Write a device driver which allocates the HMA, load it
after HIMEM.  When DOS is done processing the Config.sys, it tries to
allocate the HMA itself--if it has already been allocated, it loads
low.  You then need to free the HMA in your Autoexec (so someone else
can use it).

-- 
Adam G.
adamg@microware.com, or ...!uunet!mcrware!adamg
The above is not to be construed in any way as the official or unofficial
statements of Microware, or any Microware employees.

In article <1993Jan7.143046.22849@microware.com> adam@microware.com wrote:
> S_BUCK@rzmain.rz.uni-ulm.de (Buck Martin) writes:
> 
> >First, the question about EMM386:
> >What is the use of its L=xxxx switch? I know it's used to reserve a
> >certain amount of extended memory, but why do I have to use this
> >switch? When I have 3Mb of extended memory and want to use 1Mb of it
> >as expanded memory, I write: EMM386 1024 RAM. Is it true, that in
> >this case EMM386 takes the whole 3Mb of extended memory, changes 1 Mb
> >to expanded memory and leaves the other 2Mb unused (and inaccessi-
> >ble)? If so, what is the reason for this? If not, how does it really
> >work?
> 
> I can't find any reference to the L option in the DOS 5.0 reference
> manual.  The only options I see mentioned are RAM and NOEMS (plus the

The L option is to preserve  XMS Extended memory for other 
applications, so emm386 doesn't use it all for EMS (I think it's an
old option to preserve compatibility with CEMM (compaq EMM).

> obvious size).  When you say 1024 RAM, you are providing 1Mb of EMS
> memory (minus any memory which gets mapped into the 640-1Mb area).
> The rest is XMS (if you've loaded HIMEM).
> 
> >I'd also like to know, if there is any (shareware) expanded-memory-
> >manager for the 386 that doesn't switch the CPU to virtual mode (if
> >this is possible at all). If such an emulator exists, where can I get
> >it from?
> 
> It's my understanding that it is possible (under particular chipsets
> only) to map memory from >1Mb into the area 640-1Mb.  ie, provide UMBs
> without going into V86 mode.  It would be then possible to emulate EMS
> using XMS, although I don't believe this has been written (yet).  I
> don't really see the point, though.
> 
> >My third question is about the DOS=HIGH feature when using HIMEM.SYS:
> >Is there any possibility to prevent Mess-DOS from using the HMA if
> >there is a DOS=HIGH statement in the CONFIG.SYS? As far as I know,
> >DOS prescans the CONFIG.SYS before loading any drivers and searches
> >for a DOS=HIGH statement. If the last DOS= statement is DOS=HIGH,
> >then DOS reserves the HMA as soon as it becomes available (after
> >loading HIMEM.SYS).
> >Does anybody know, how to force DOS into low memory though there is a
> >DOS=HIGH statement (it must be possible; I've seen 2 multi-configura-
> >tion-programs doing this)?
> 
> You betcha.  Write a device driver which allocates the HMA, load it
> after HIMEM.  When DOS is done processing the Config.sys, it tries to
> allocate the HMA itself--if it has already been allocated, it loads
> low.  You then need to free the HMA in your Autoexec (so someone else
> can use it).
> 
> -- 
> Adam G.
> adamg@microware.com, or ...!uunet!mcrware!adamg
> The above is not to be construed in any way as the official or unofficial
> statements of Microware, or any Microware employees.
-- 

Mark Simonton       // ::test(MS-DOS);
-{;-> marksi <-:}-  ...!uw-beaver!microsoft!marksi
			marksi@microsoft.com

>> It's my understanding that it is possible (under particular chipsets
>> only) to map memory from >1Mb into the area 640-1Mb.  ie, provide UMBs
>> without going into V86 mode.  It would be then possible to emulate EMS
>> using XMS, although I don't believe this has been written (yet).  I
>> don't really see the point, though.

A program called UMB_DRVR does this.  Check for it at Simtel-20.

-- 
#ifdef TRUE        | Fuzzy Fox (a.k.a. David DeSimone)       fuzzy@netcom.com
#define  TRUE   0  |
#define  FALSE  1  |  "911 Emergency Rescue Service - Can you hold, please?"
#endif             |

In article <1993Jan7.081002.1841@wega.rz.uni-ulm.de>, S_BUCK@rzmain.rz.uni-ulm.de (Buck Martin) writes:
> I need some information about Mess-DOS 5.0's EMM386-driver and the
> DOS=HIGH feature.
> 
> I'd also like to know, if there is any (shareware) expanded-memory-
> manager for the 386 that doesn't switch the CPU to virtual mode (if
> this is possible at all). If such an emulator exists, where can I get
> it from?

Uh, unless you have a motherboard chipset that supports hardware EMS,
no way.  Virtual mode is the only way you can enable the paging feature
needed to emulate EMS on a 386.

 
> Does anybody know, how to force DOS into low memory though there is a
> DOS=HIGH statement (it must be possible; I've seen 2 multi-configura-
> tion-programs doing this)?

Uh, DOS=HIGH means just that!  It tells DOS to load HIGH.  If you don't
want DOS to load HIGH, don't use DOS=HIGH!  The HMA is still available
to other software as long as HIMEM.SYS is loaded and DOS is not loaded
high.

As far as I know, EMM386 only uses the memory you tell it to use.  However,
it allocates this memory from the XMS pool (which HIMEM.SYS manages).  OLD
programs that try and access extended memory directly without using XMS
services won't see any if HIMEM is loaded.  New software uses HIMEM
to manage extended memory as "XMS" memory and all is happy.

-john r pierce
hacker at large