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Q141682: How to Change Memory Allocations for Macintosh Programs

Article: Q141682
Product(s): Microsoft Tips for the Macintosh System
Version(s): MACINTOSH:
Operating System(s): 
Keyword(s): 
Last Modified: 22-APR-2001

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The information in this article applies to:

- Apple Macintosh System Software 
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NOTE: This article applies to Mac OS versions earlier than Mac OS X (Mac OS 9.1 and earlier).

SUMMARY
=======

On a Macintosh computer, you can manually adjust the amount of memory the system
allocates to a program. However, the amount of memory that the program actually
gets depends on several factors. One of these factors is the amount of memory
available in the largest unused block. If the system is low on memory in the
largest unused block, the program may not start or it may quickly run out of
memory when you try to open a file or perform actions such as copying or pasting
data.

MORE INFORMATION
================

Programs on a Macintosh have two memory settings that can be adjusted: Minimum
size and Preferred size.

The Minimum size setting indicates the smallest amount of memory that will be
requested by the program when it is started. If the largest unused block of free
System memory is less than the setting for the program's Minimum size, the
program will not start.

The Preferred size setting indicates the total amount of memory requested by the
program. The system will give as much of the largest unused block to the program
as it can, up to the amount specified for the program's Preferred size.

In addition to preferred and minimum memory sizes, programs have a third memory
requirement called "suggested size." Suggested size is a number that is set by
the developers of your program and cannot be adjusted. Suggested size is the
amount of memory that the program developers felt the program would run best
with: you should always try to set the Preferred size to a number at least as
large as the suggested size.

To better understand the differences, see the following examples.

  Example 1
---------

  Minimum size: 2048K
  Preferred size: 4096K
  Largest unused block of System memory before starting program: 1800K

  In this case, the program will not start because the largest unused block of
  free system memory is less than the minimum size for the program.

  Example 2
---------

  Minimum size: 2048K
  Preferred size: 4096K
  Largest unused block of system memory before starting program: 3000K

  In this case, the program should start, but it will only be allocated roughly
  3000K of memory. It will try to get as much as it can, but it can only get up
  to the amount in the largest unused block of system memory.

  Example 3
---------

  Minimum size: 2048K
  Preferred size: 4096K
  Largest unused block of System memory before starting program: 8000K

  In this case, the program should start, and it should get all of the 4096K
  requested of the system. It probably won't be using all of this 4096K,
  though, as there is usually quite a bit of extra room for your personal data
  files to be loaded into memory by your program.

Note, in all cases, the largest unused block of system memory may be much lower
than you think because of memory fragmentation. This article will not discuss
memory fragmentation. However, note that to clear up most problems with memory
fragmentation, shut down all running programs and restart your computer.

How to Determine Unused System Memory and Program Memory Requirements
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In order to configure memory allocations for various Macintosh programs, you must
know where the memory settings are located.

To determine the largest unused block of system memory, click About This
Macintosh on the Apple menu.

  NOTE: If you do not see "About This Macintosh", but instead see "About
  <program name>", then click "Hide <program name>" on the
  Application menu and then repeat click About this Macintosh on the Apple menu
  again.

In the About This Macintosh window, you should see the version number of the
System Software. You should also see the amount of memory taken up by the
System, a list of currently running programs, the amount of memory allocated to
each program, and a number for the largest unused block of system memory. If the
sum of all of these memory amounts is much less than the number that is shown
for Total Memory, you probably are running into a situation of memory
fragmentation.

To set the memory requirements for your program, do the following:

1. If your program is running, save any of your files and quit the program.

2. Locate the icon for your program on your hard drive and click once on it to
  select it.

  NOTE: You must locate the actual program icon rather than an alias for the
  program (you cannot do the next steps from the icon for the alias).

3. With the program icon selected, click Get Info on the File menu.

4. In the "<program name> Info" window, click the edit box for either the
  Minimum size or the Preferred size, delete the current number, and enter the
  new amount.

5. After you have made changes to either the minimum size or the preferred size,
  or both, close the window and restart your program.

You do not have to restart your computer for the above changes to take effect.

For additional information about Memory Requirements on a Macintosh, please see
the following article(s) in the Microsoft Knowledge Base:

  Q127084 Power Mac Applications Require Less RAM with Virtual Memory

  Q120506 How Virtual Memory Works on a Power Macintosh

  Q139406 MXL5: Macintosh System Memory Requirements


Additional query words: mac powermac

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Keywords          :  
Technology        : kbHWMAC kbOSMAC kbMSNonProductSearch
Version           : MACINTOSH:

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