Re: Memory management FAQ

On Fri, 25 Oct 2002 [email protected] wrote:

> Hi all, I am sure I am no the only one who is getting totally lost in
> the discussions on memory management.  What a humble user
> like myself could do with is a simple FAQ style document showing
> me how to set up the various memory management combinations
> (with sample autoexec.bat and config.sys files as appropriate)

I'll try to be short and basic here:

if you have only an XT (8088) there is nothing you can do, except for
removing drivers, reducing BUFFERS etc. ~500000 bytes free, not more.

if you have an AT (286) with a fair amount of memory (at least more
than 640k) then you can use for CONFIG.SYS
a)
DOS=HIGH
DEVICE=FDXMS286.SYS
and use the XMS-swapping command.com
That way you have ~620000 bytes free, but all drivers you load (ctmouse,
nansi, ...) are going to be in conventional RAM, thus eating from those
620000 bytes.

if you have a 386SX or better _and_ you want to run DOS32 programs and
none of your programs need EMS then you can use
b)
DOS=HIGH
DEVICE=FDXMS.SYS (<64M) or DEVICE=FDXXMS.SYS (>64M memory) or
  DEVICE=HIMEM.EXE (if you feel like it)

and use the XMS-swapping command.com.
The situation for DOS memory is the same as for a)

Now if you don't want those drivers eating away from conventional RAM
then you can use
c)
DOS=HIGH,UMB
DEVICE=HIMEM.EXE
DEVICE=EMM386.EXE
DEVICEHIGH=C:\BIN\NANSI.SYS
...
SHELLHIGH=COMMAND.COM

BUT then you cannot use DOS32 program (unless you use some other
non-free EMM386-like program instead).

The technique with UMBPCI is a variation between b) and c)

d)
DOS=HIGH,UMB
DEVICE=FDXMS.SYS (<64M) or DEVICE=FDXXMS.SYS (>64M memory) or
  DEVICE=HIMEM.EXE (if you feel like it)
DEVICE=UMBPCI.SYS
DEVICEHIGH=C:\BIN\NANSI.SYS
...
SHELLHIGH=COMMAND.COM

This only works if UMBPCI supports your motherboard chipset.
In this case you have no EMS (unless you get the EMS simulator from
Simtel), but you can run DOS32 programs.

In general, using the XMS-swapping FreeCOM, situation b) isn't nearly as
bad as it used to be. Only if you need a few large device drivers you will
get into trouble.

Bart