Category : Pascal Source Code
Archive   : INFOS155.ZIP
Filename : PAGE_03.INF

On this page, INFOPLUS displays how your RAM is being used.

Total conventional memory: This is the type of memory typically used by DOS
and programs.

Free conventional memory: This is the amount of memory left after DOS,
drivers, and TSRs take some. INFOPLUS does not
count itself as using any.

Extended memory: This is the amount of memory on a 286/386/486 that is
above the 1 Meg mark. This may not be the total amount.
Some programs that use extended memory subtract what they
use, and report that to INFOPLUS. Also, programs such as
QEMM and HIMEM.SYS will 'steal' all of it because they
want to manage it in a way that allows different programs
to share it. If you use a memory manager, this will
probably be 0K.

XMS driver: One of the major problems with extended memory is that there
was no correct way of accessing it. There were major problems
with programs interfering with each other. XMS stands for
eXtended Memory Specification. It's a standard interface for
programs to access extended memory.

HMA stands for High Memory Area. On a 286/386/486, it's
possible to access the first 64K of extended memory without
going into a special CPU mode. Access to that area is done by
enabling or disabling A20 (address line 20.) DOS 5 is capable
of placing some of it's code and BUFFERS in the HMA. Infoplus
tell you if it is using it, and how much is left over (or being
wasted, depending on your point of view!)

The XMS driver also handles Upper Memory Blocks (UMBs).
Infoplus will display if any area is available, and how big the
largest block is.

DPMI driver: With the growing complexity of programs, some need more than
the normal 640K of memory to run. DPMI stands for DOS
Protected Mode Interface. It allows programs to run in
protected mode, yet still access regular DOS functions. It was
introduced with Windows 3, and offers greater protection from
interference by other programs than VCPI. DPMI is available on
286/386/486 computers.

Expanded memory: Expanded memory was one of the first ways of getting more
than 640K in a computer. It does this by taking the extra
memory and breaking it up into 16K 'pages.' It puts up to
4 of these at a time in a 64K window in an unused area of
memory accessible to the CPU (called the page frame.)
Expanded memory is often called EMS (Expanded Memory
Specification.)

All EMS drivers have an internal driver name of EMMXXXX0.
The latest specification is 4.0. Unfortunately, 4.0
requires some hardware specifics for FULL compliance. Many
4.0 drivers are not hardware compliant. Their hardware is
in compliance with the older standard, version 3.2.

Some EMS drivers also support VCPI (Virtual Control
Program Interface.) This was the first standard to allow
programs to run in protected mode, yet still access DOS
functions. Unfortunately, it's too easy for programs to
interfere with each other, or unncessarily block another
VCPI program from working. VCPI is only available on
386/486 computers.