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1993-06-14
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Chapter 1
Advanced Information
1.1 IRQ conflicts: Or why your system acts like it has the
shakes.
IRQ conflicts are a hidden source of numerous nasty problems with
running DOS. As more and more hardware is installed in the
backplane, the chances of a conflict are very high. Herewith
follow Firefly Software's "rules of thumb".
Get rid of internal fax and modem cards. Make external any
hardware that can be.
Turn OFF the IRQ for LPT1 & 2. The IRQ is not needed unless you
use the printer ports for 2 way processing, and very few
installations do. Ordinary printing does not use bi-directional
transmissions.
Remove the IRQ from COM2. Since I use COM2 only for a debug dump
line, consequently it does not seem to suffer from having the IRQ
turned off.
These measures will free IRQs 3,5,7.
Consult your hardware manual for instructions on how to disable
the IRQ's. Usually they are turned on/off by dip switches.
1.2 Expanded Memory (EMS): Or how to get along without knowing
what you are doing until the hair is all gone.
This comes under the heading of topics that you think you know,
what is going on. But in reality the tip of the iceberg is all
that is really visible. Stand here at the edge, and peer down
into the depths. The wonders to behold.
There are basically 3 memory managers.
1. 386Max
2. QEMM
3. EMM386
The following information is NOT inclusive, in that the material
will be confined as much as possible to EMS, and only 386
machines.
These memory manager provide control of EMS, XMS and UMB.
1. Expanded Memory
2. Extended Memory
3. Upper Memory Blocks
In general, if the memory manager provides EMS, it will also
provide the same total space as XMS memory, if requested. This
means that 1 meg of space can be used as EMS or XMS. Requests for
both being drawn from the same pool, up to a combined total of 1
meg.
If EMS is turned off, or inactive, there will not be any XMS.
If the UMB is turned on then the manager will provide upper
memory blocks for use by DOS.
If the memory manager is not loaded into memory it is the same as
if the manager were turned off. Except, in some cases EMS API
calls will appear to succeed, if loaded but not active.
If MS Windows is loaded after these memory managers, it turns
them off and provides the support. Except, there will no UMB
support if it was turned off prior to Windows' loading. This
means that Windows will provide EMS and XMS even when the other
memory managers were not loaded or active before Windows started
up.
If the NoEMMDriver switch is TRUE in system.ini, then Windows
will not provide EMS or XMS support. Even if a PIF file provides
such.
A DOS application which fails to open "EMMXXXX0" and check the
returned file handle to see if it is a device, and subsequently
attempts to make EMS calls may experience calls that may or MAY
NOT fail. Some older EMS using programs do not check this
properly. When they fail, it is likely to be with a General
Protection Fault!
- 2 -
A DOS application running in Windows, where the PIF did not
provide any EMS will sometimes report a page frame segment of
B000 hex!
Configuration parameters in effect before Windows starts will be
taken over by Windows. You can not override these parameters with
those in system.ini.
*************************************************
There may be mistake in the text above, in that Windows will not
provide EMS if there was no EMS frame enabled before Windows was started.
- 3 -
Contents
Chapter 1 Advanced Information 1
1.1 IRQ conflicts: Or why your system acts like it
has the shakes. . . . . . . . . . . . . . . . 1
1.2 Expanded Memory (EMS): Or how to get along
without knowing what you are doing until the
hair is all gone. . . . . . . . . . . . . . . 1
i