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Q66513: Memory Requirements for Real-Mode CodeView (CV.EXE)

Article: Q66513
Product(s): See article
Version(s): 3.00 3.10 3.11 | 3.00 3.10 3.11
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | | mspl13_basic
Last Modified: 11-NOV-1990

Real-mode versions of CodeView (CV) beginning with version 3.00 offer
a number of ways to utilize available memory in order to make the
greatest amount of conventional memory available to the program being
debugged. The amount of memory actually used depends on the
command-line options specified as well as the configuration of the
system used for debugging.

The following table shows the size of CodeView in standard DOS memory
with each of the memory-specific command-line options (see the "More
Information" section below for further details):

   Option  RAM Usage                   Option  RAM Usage
   ------  ---------                   ------  ---------

    /X       16K                       /D16     210K
    /E      192K                       /D32     225K
    /D      256K (same as /D64)        /D128    320K

The following descriptions of the three memory-related CodeView
options explain the ways in which each option affects memory
utilization in addition to the respective amounts of conventional
memory that CodeView requires with each. (This information pertains
only to CodeView versions 3.00 and later -- versions of CodeView
earlier than 3.00 require approximately 230K of RAM specifically for
CodeView.)

/X - Specifies that CodeView should utilize extended memory. Assuming
     that enough extended memory is available, this option moves both
     the symbolic information and most of CV itself into extended
     memory. Allowing CV to be loaded into high memory requires that
     approximately 16K to 19K of "control" code remain in conventional
     memory, thus all free conventional RAM over 19K is available to
     load the program to be debugged (the "debuggee").

/E - Specifies that CodeView should utilize expanded memory. Assuming
     that enough expanded memory is available, this option moves both
     the symbolic information and CodeView's own overlays into
     expanded memory. The size of the CV "root" without the extra
     overlayed code is approximately 192K. Since the overlays do not
     cause any additional overhead with /E, all free conventional RAM
     over 192K is available to load the debuggee.

/D - Specifies that CodeView should utilize disk overlays in
     conventional memory. By default, this option creates a 64K buffer
     area for loading disk overlays. With the 192K root, the 64K
     buffer means CV will take about 256K of conventional memory with
     /D. In addition, the symbolic information must also be loaded
     into conventional memory; therefore, since symbolic data varies
     with each program, it is not possible to specify the amount of
     memory available for the debuggee alone.

     The /D option can also be specified with a value that indicates
     the size of the overlay buffer area. This parameter can be any
     value from 16 to 128, which represents an overlay buffer size
     from 16K to 128K. Specifying /D16 will minimize CodeView's size
     with disk overlays to approximately 210K. This maximizes the
     amount of conventional memory that will be available to load the
     debuggee and the symbolic information. At the other extreme,
     /D128 causes CV to use approximately 320K of conventional RAM.
     This provides faster CodeView execution speed, but it will only
     work with smaller debuggees.

Note: CodeView will default to the best memory usage possible. In
other words, if NO memory usage option is specified, CV will try to
use extended memory. If extended memory is unavailable, CV looks for
expanded memory. CV will use disk overlays on its own only if expanded
memory is not found.

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