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PAGE_03.INF
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1991-06-04
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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.
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 correctly.
XMS driver: One of the major problems with extended memory is that there
was no correct way of accessing it. There was a major problem
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.)
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, numbered 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.