Managing your Memory

Introduction:


Your Macintosh comes with 4 Mb or more of Random Access Memory (RAM), which is the working memory of the machine, the space that the programs and data run in. You can check how much memory you have, and how it is being used; while you are in the Finder (i.e., not running a program) go to the Apple Menu, and pull down to "About This Macintosh" or "About The Finder". This will give you a screen that shows how much total memory that you have (in Kilobytes - 1024 Kilobytes (Kb) equals 1 Megabyte (Mb)). This screen will also show you which programs are currently running, how much RAM they are using, and the size of your largest block of free RAM. The System will always be running, and it will consume a variable amount of RAM, depending on a number of settings.

Adjusting Application Memory Size:


Each Macintosh program has a suggested memory size. This is the amount of RAM that the System will reserve for that program when the program is started. You can adjust the allocation, in order to either give more room for large projects, or to reduce the allocation to conserve RAM for other programs. You adjust the application memory size by locating the programs icon on your hard drive (the program must not be running at the time), click once on the icon, and either type Command-I or choose Get Info from the File menu. A dialog box will appear with information about the program, and at the bottom of the box, there will be a "Suggested memory size" figure, and under that, a box into which you can enter your desired Application memory size for that program. Some programs run better if you increase the memory size above the suggested size. It is generally not a good idea to set the allocation below the suggested amount. These settings and their effects will vary from program to program.

Trimming your memory:


Sometimes you run into a situation where there isn't enough memory to run all the programs that you want at the same time. You may get a message such as "There isn't enough memory to launch Program X". There are several things that you can do, including turning on Virtual Memory (if you have a Macintosh with a PowerPC or 68030/040 processor chip) and installing extra RAM chips into your machine. But first, follow these general guidelines to trim your memory usage:

  1. Make sure that there aren't any programs running that you don't need. Often, you can close a document, and you assume that you have quit the program, but the program is still running and taking up RAM. Programs generally don't quit until you specifically use Command-Q or Quit from the File menu. Look under the icon on the top right of your screen (System 7.0 and up) or the bottom most entries under the Apple Menu (System 6.0x) to check which programs are running. Go to any programs that are not needed, and Quit to free up the RAM that they were using.

  2. Check the application memory size of the program that you are trying to launch (as above) to make sure that it isn't larger than necessary.

  3. Turn on Virtual Memory in the Memory control panel in Control Panels under the Apple Menu and re-start .

  4. If you have been going in and out of a number of programs, your memory may be fragmented. Re-starting will solve this.

  5. Put your System on a diet. There are many features of the Macintosh System, some of which are important to the way you use your Mac and some of which aren't. Add-on utilities, control panels, INITs and Extensions also use up some RAM for their functions. All of this contributes to the large memory consumption of the System. You can tailor your System for efficient memory use. Here are some guidelines.

    • Check the Cache setting in the Memory Control Panel. Generally a setting of 32Kb or 64 Kb is adequate. If it is higher, lower it and this will free up RAM.

    • If you are using Adobe Type Manager, OnLocation, Norton FileSaver, Suitcase II, Mirror, AutoDoubler, or MacTools, each of these have caches. Go into their respective control panels and either turn the utility off or lower their cache settings. Refer to their manuals for instructions. Re-start to make the changes take effect.

    • Remove unneeded printer drivers and extensions. (The following describes specific System 7.0 features. System 6.0x machines are similar). Some of the features of the Macintosh probably arent being used with your particular set-up, primarily in the areas of printing and networking. We will assume for the moment that you are not networked to another Macintosh or connected to a mainframe. If you are, you will need to leave in some of these items.

      Open the System Folder on your hard drive (there should only be one. If you have two , you will experience problems and should call your dealer or Macintosh support contact for assistance). The System 7.0 System folder has the following folders in it, and you can remove the items as indicated. Don't throw them in the trash, but rather create a new folder for them outside of the System Folder and drag the unwanted items to the new folder.

      • Extensions Folder:
        Remove every printer driver except for LaserWriter and the driver for whatever other printer that you use. You can probably get rid of AppleTalk ImageWriter, LQ ImageWriter, Personal LaserWriter SC, plus ImageWriter (if you dont own one). Remove File Sharing Extension, AppleShare, EtherTalk, DAL, Network Extension, and A/Rose (you may not have had all of these on your machine to start with).

      • Control Panels Folder:
        Remove Easy Access, Sharing Setup, Map, File Sharing Monitor, and Users and Groups. If you have a desktop machine, remove Portable, PowerBook, and AutoRemounter.

      • And finally, if you have any shareware or third party utilities or Extensions installed which you can live without, particularly sound playing programs or screen savers, remove them. Youll save RAM and your machine will perform better. When it comes to System Folder contents, less is better.

  6. Re-start your Macintosh after making these changes.

Fragmented memory:
Sometimes, you will see that the "Largest Unused Block" of memory in "About This Macintosh" is smaller than the total memory less the sum of the memory used. This is because you have opened and closed some programs, while some programs are still running. This has left some gaps in the memory, where there is some free RAM "in-between" programs that are still running. The available RAM is limited to what is in a continuous block, so if the memory is fragmented, there may not be enough of a block available to open another program. To remedy this, you can either re-start your Mac, or you can quit from every program that is running, and then re-open the ones you want.

32 bit addressing:
If you have more than 8 Mb of RAM installed in your Macintosh, you will need to go to the Memory control panel and turn on 32-Bit Addressing or Modern Memory Manager in order to access the memory above 8 Mb. Some older programs, particularly games and shareware, have difficulty with 32-Bit Addressing, so you may want to keep a note of which ones that you have, and switch 32-bit addressing off before using these programs. Re-start to make the change effective.

Virtual Memory:
Virtual Memory utilizes a section of your hard drive to mimic RAM, so that your programs can use more RAM space than you actually have. This is available only with System 7.0 on more recent Macintoshes with PowerPC or 68030/040 processor chips, and is not recommended for PowerBooks due to the battery drain from accessing the hard drive all the time. Virtual Memory is turned on in the Memory control panel. Virtual Memory is quite a lot slower than real RAM, so should be used only when absolutely necessary. The exception to this rule is the PowerPC series of Macintoshes. If you turn on Virtual Memory, then set it to the lowest amount (1 Mb more than the amount of actual RAM that you have), then PowerMacintosh native software will use RAM more efficiently when it loads.

Using Virtual Memory will cost you some hard drive space, a space equal to the amount of real RAM that you have plus the amount of extra Virtual Memory that you are adding. Virtual Memory should not be used with Adobe PhotoShop, which has its own VM software.

RAMDoubler: There is a program called RAMDoubler, which improves upon Apples Virtual Memory scheme. RAMDoubler compresses the amount of memory that your inactive programs take while they are idling in the background, and RAMDoubler has advanced hard disk virtual memory management, which combine to fool your Mac into thinking that it has double the RAM that it actually does. There are a few software conflicts with RAMDoubler, and it should only be used with 68030/040 and PowerPC Macs that have 8 Mb or more of real RAM. RAMDoubler is best for people who tend to keep several programs open at once, using many relatively small files. It is not much help when you are using one program with a single large file, so it is not recommended for use with Adobe PhotoShop.