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RAM Charger 8 HTML Manual


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This section provides optional, general information about your computer's memory and will help you get the best results from RAM Charger. The short-term memory being charged is often called RAM (after the Random Access Memory hardware it is built from)-- and is very different from long-term disk storage--but we will simply call it memorythroughout this manual.


Memory used by
application software

Whenever an application is used to perform some function or to display anything in a window, a collection of instructions and data (sometimes called resources) must be loaded into memory. Normally, on a Macintosh, all the memory that an application may use during a session is reserved for its exclusive use when it is first launched.6Applications can be launched either by opening the application itself or by opening a document created by the application.


Memory requirements
of open applications

The amount of memory reserved for an open application is defined by the application's author, but may be changed by the user before the application is launched. The memory requirements of an application are shown in the RAM Charger Application Settings window, in RAM Charger's Application Info window, or in the Finder's Get Infowindow.

Without RAM Charger, all of an application's anticipated memory needs must be reserved, when it opens, and locked in a single continuous block of memory. In addition, this block cannot be repositioned in memory and it cannot grow or shrink in size. This causes inefficient use of memory and limited flexibility when using the application.

Since the reserved size must anticipate anything the user might do, there is often memory which sits idle during normal or simple operations. That means it's wasted, since it cannot be used by other software. On the other hand, there might not be enough memory reserved when the need arises for large documents or complicated operations, even if there is plenty of unused memory outside of the application's block.

However, when RAM Charged, the amount of memory varies dynamically, up and down, while the application remains open. So, RAM Charger allows applications to launch with a smaller starting size but then not be limited to it. They can grow much larger, when and where they need to, because RAM Charger gives them access to all the unused memory in the machine, as if it were already reserved in each application's block.


Applications slow to
release unused

Some applications might allocate additional memory when needed, but then not release it immediately afterwards (for example, when opening and then closing a document). In some cases this might be just an oversight in the design of the application but in others this behavior might be used to improve performance. RAM Charger encourages applications to take full advantage of all the memory at their disposal until it is needed to fill another request. Since RAM Charger can sometimes recover memory being held by one application when needed by another, this means the amount of memory that can actually be accessed at a given time could be more than the total knownto be available (shown as Total Unused Memory).

However, there are a few applications that hold on tightly, so unused memory is not released even when it's needed elsewhere. When RAM Charged, such an application might still start out small, grow when it needs more, but then not shrink back as soon as it needs less. There is a RAM Charger option, called Squeeze, that can help in some of these cases. For example, this allows Excel 5.0 to maintain its best performance by using lots of memory that's available and then release it when another application is opened or brought to the front.


Applications that take
memory before

It is possible that a RAM Charged application, when given access to as much memory as it needs, will simply take it all--even if it doesn't need it right at the moment. In order to accommodate as many different "greedy" applications as possible, there are several RAM Charged methods that have been designed to limit such an application without having to use it UnCharged and without eliminating all the benefits of RAM Charging it . For a more detailed explanation on how to handle "greedy" applications, please refer to Fine Tuning Applicationsin the Customization section.


Memory used by
system software

Memory is needed to support a variety of "system" functions, in addition to application needs described above. This includes storage of common instructions and data which might be needed by any software (for example, in support of different fonts, or for accessing files and folders on disks). It also includes memory for a variety of other things, such as the Finder, networking and other system extensions, desk accessories, and control panel windows.


Blocking expansion
of system memory

The allocation of system memory is not managed by RAM Charger because it already grows and shrinks dynamically, based on need. Unfortunately, it is not quite as flexible as a RAM Charged application. There can be situations when an operation cannot be completed because of not enough system memory-- when the system memory is blockedfrom expanding-- even though there is plenty of unused memory elsewhere in the machine.

RAM Charger reduces the problem of system memory being blocked in three ways:

  • First, it reduces the blocking itself by keeping a specified amount of memory next to the system heap unused.
  • Second, it displays the current availability of memory for system use to help you anticipate blocking and avoid it before it happens or to help you resolve it more quickly when it does.
  • Finally, when not enough memorysituations are reported, RAM Charger reports additional information about the situation and can often identify the particular application whose memory is blocking system expansion. Closing windows or quitting the blocking application can remove the blockage.

Here is why system memory can become blocked: The dynamic system needs are provided from an area of memory called the System Heap. This is one continuous block of memory that has a movable boundary at one end so it can change size as needed. However, it can only expand if the memory past its movable boundary is currently unused. In order to stay flexible, this memory neighboring the system heap is normally the last to be assigned for other use.

However, the situation can arise (and all too frequently in some user's configurations) where the memory next to the system heap is in use even though there is plenty of unused memory elsewhere. This effectively blocks expansion of the system. So the user might be told that there is not enough memory to keep a Finder window or a control panel open (such as RAM Charger's) even though other indicators say there is plenty available.


Reducing memory
used by system

If you still find situations where you don't have enough memory to open the applications and/or documents you need, there are other measures you can take before upgrading your hardware. Most of the following suggestions involve reducing the amount of memory

used by your system software in order to leave more available for your application programs and documents. When removing items from your system, be sure to drag the items to a location outside the System Folder and save them in a separate folder (named "System Extras," for example) so that you can use them later if necessary.

  • Turn on 32-bit Addressing in the Memory control panel (in most of the newer Macintosh models, this cannot be changed). If you have more than 8 megabytes of memory, this can make a lot more memory available to your programs. The only downside to this is that you might have some older software that doesn't work correctly (if it is not "32-bit clean"). This should not be a problem with any current versions of commercial software.
  • If you are using a Power Macintosh computer, turn on virtual memory in the Memory control panel. Apple recommends that you do this, even if you do not require a lot more memory, because it will allow much more flexible and efficient management of the memory that is used by most of your Power Mac native applications. And, if you set the increased size of virtual memory as small as possible, it will have little impact on the performance of your system. There are a few software products that are not compatible with virtual memory techniques and, if you need to use one, you will have to leave virtual memory off.
  • Turn off the RAM Disk in the Memory control panel.
  • Reduce the disk cache size in the Memory control panel. (Be aware that setting this too low can reduce performance.)
  • Remove File Sharing Extension from the Extensions folder in the System Folder (if you don't need to share any of your files over a network).
  • Remove from the Extensions and Control Panels folders, inside the System Folder, any third party enhancements which you do not need. (You might wish to remove these one at a time, in order to find out how much memory is used with each one.)
  • Reduce the cache size in ~ATMTM, AutoDoublerTM, or other third party control panels that have an adjustable cache. (Be aware that these sizes can impact system performance.)
  • Turn off AppleTalk® in the Chooser (if your computer is not on a network or using an AppleTalk printer).
  • Remove the PC Exchange control panel from the Control Panels folder inside the System Folder (if you don't need to use disks or documents from DOS computers).
  • Remove ProDOS® File System from the Extensions folder inside the System Folder (if you won't be using Apple II disks).
  • Remove items with "CD" or "File Access" in their names from the Extensions folder inside the System Folder (if you aren't using a CD-ROM drive with your computer).
  • Remove QuickTimeTM from the Extensions folder inside the System Folder (if you aren't using a CD- ROM drive or video images that require QuickTime with your computer).
  • Whether you use a Power Macintosh or not, you can expand the space available for programs by turning on Virtual Memory in the Memory control panel (not available on some models). To do this, follow the instructions in Using Hard Disk Space as Memoryin the Macintosh User's Guidewhich came with your computer. (Be aware that the larger you make your virtual memory, and the more fully you utilize the additional space, the slower the computer will perform.)

Running out of

When a RAM Charged application finally needs more memory than is available, you can often free up the memory required by closing other windows or quitting other programs. RAM Charger allows you to continue your work by using any newly freed memory even if it is released by a different application.

To continue without RAM Charger, you would normally need to quit the application and reset its size. Then you would have to quit one or more other applications in order to reopen the first with the larger size. Very likely you would even have to restart the computer if free memory was fragmented into blocks smaller than the required new application size. Finally, you would have to reopen your work before you could retry the aborted operation (if you could still remember what it was).

There are some application operations that just can't recover when the free memory they require is not available in their program partition. So they quit unexpectedly, without giving you a chance to save your work. This is known as a "crash" or "bomb." RAM Charger helps prevent such crashes, because it insures that all the free memory in the computer must be used up before a RAM Charged application can run out. And, a low memory caution signal (described fully in the Feedbacksection) gives you early warning so you can often avoid running out entirely.

RAM Charger takes the additional step of identifying certain memory requests whose impending failure will cause a crash, and gives you an opportunity to free up the required memory to avoid the crash. (This is not to say that RAM Charger is able to eliminate allsuch crashes, so you should still save your work regularly!) RAM Charger will notify you and suspend the program's operation so you can switch to other programs, to quit them or close windows, and free the needed memory. If the program that needs memory is the active program, then you will get an alert explaining the problem and how to proceed. When you acknowledge the alert, the program will hide its windows and suspend operation so that you can switch to other programs and free memory by closing windows or quitting. When there is enough free memory for the suspended program to continue, the RAM Charger green signal light will flash over the application menu to notify you that you can reactivate the suspended program (marked with a diamond in the application menu) and continue your work. If this type of impending memory problem is detected while the RAM Charged program is in the background (not currently the active program) then a red signal light will flash over the application menu to notify you of the situation. Then, when you select the diamond-marked application from the menu it will display the descriptive alert and proceed as described for an active program.

If a program that needs more memory is not important and you don't need to save any work being done in it, you may prefer to simply force it to quit, when alerted to its need, by pressing the Command-Option-Escape combination on the keyboard. (Although forcing a program to quit in this manner is a rather extreme measure to take, you can often use this technique successfully with any active program--including the Finder in some system versions--when there is no other alternative to free enough memory to save your work.)

Some programs could mistakenly determine that there isn't enough memory for their operations, even when RAM Charger is able to supply their needs. If you are alerted to a shortage of memory when you feel there should be plenty available for the task at hand, you may be able to proceed by simply retrying the operation. If not, you may be able to do so after performing some other intermediate task. If the program is still unable to get the required memory, you may wish to try some of the adjustments described in the Advanced RAM Chargersettingssection before resorting to disabling RAM Charger for the individual program.

Important safety note, whether you use RAM Charger or not:Some programs, which are generally very reliable and otherwise bug-free, may have problems when running low on memory. Also note that when a malfunction occurs, it can easily corrupt other programs that are open, and even affect the system code and data. Therefore, whenever you wish to be as safe as possible with your work, it is a good idea to save everything and restart the computer if any program crashes or quits unexpectedly, or if you suspect that any program has been malfunctioning.


6. The term launchmeans the same as terms commonly used with other computers, such as run, execute, and load,and the same as the more general term open, when applied to applications.


(RBackgroundA -- 03/17/98)

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Copyright © 1995-98 Jump Development Group, Inc. All rights reserved. Jump, OptiMem, RAM Charger, and More About This Mac are trademarks of Jump Development Group, Inc. Apple and Macintosh are registered trademarks of Apple Computer, Inc. All other trademarks are the property of their respective holders.