The amount of main memory (RAM, Random Access Memory) installed in a computer can be very important for the system’s achieved computing performance. If not enough memory is available, the speed of the computer will significantly decrease. If too much memory is installed, capacities that are not really needed will be left unexploited. Unnecessary costs will be the result.
Which memory size is the optimum will depend on how you use your computer, in particular, which applications you are using, which data is processed by the applications, and to which degree programs are being used simultaneously, causing them to be held in memory at the same time. Mac OS X keeps very detailed internal statistics how the amount of available memory is used by each of the programs. TinkerTool System can evaluate these statistics to assess whether the size of RAM installed in your computer is appropriate for your typical work. This will give you an important aid to decision-making if you should purchase more RAM for your computer, and if additional memory will actually enhance performance.
Like in any up-to-date operating system, no running program has the permission to access main memory directly. This is left to the inner core (kernel) of the operating system only. For each running program (also known as process), the hardware simulates a separate memory space. Each process runs in its own, completely separated area which appears to be exclusively owned by it. The memory spaces of other processes are completely invisible for the process in focus. With this approach, a process is neither capable of spying out the data of others, nor can it intentionally or unintentionally overwrite data in the spaces of other processes. This is one of the most important techniques which ensure that an operating system is stable and safe. Programs are strictly shielded against each other. Even “bad” applications cannot crash other processes or the operating system.
This technique is called virtual memory. It is essentially managed by a hardware component inside the processor, called Memory Management Unit or MMU. For each access to (virtual) memory, the MMU decides which memory should be actually accessed internally: Virtual memory is either being mapped to real main memory, or to special files on the system disk, the so-called swap space. Mapping virtual memory to real memory is done in blocks, organizational units that are called pages. With Mac OS X, each page always has a size of 4 KiB.
The system tries to map virtual memory to real main memory as long as possible. However, if too many processes are running simultaneously, or too much data is being processed at the same time, the amount of main memory available will no longer suffice at one point to host all pages of needed virtual memory. In this case, a page from main memory will be transferred to disk to make room. To do this, the system selects a memory page which is very likely not required by any process in the near future. By transferring a page of memory contents to disk, a block of memory in RAM has now become free and can be used by another process. When a page on disk is later being accessed by the process associated with it, it has to be transferred back into main memory. Another page will now be selected to be thrown out, and the two pages swap places.
Because main memory and hard drives work with very different speeds, access to paged-out memory can be 10,000 to 100,000 times slower than accessing memory in RAM. For this reason, the perceived speed of a computer can decrease drastically if too many page-outs take place, i.e. there is not enough main memory to hold as many of the used memory pages in the quickly accessible area as necessary. The theoretically best usage of memory has been reached when main memory is being used completely (no memory is free), and no swap space is in use. In this case, all data will be in the fast RAM and no part of the RAM is left unexploited.
As already mentioned, assessing the amount of memory is only possible when relating it to the typical usage of memory during the daily work with your computer. Whether you have enough memory will depend on what applications you are using and how you are using them. For this reason, a meaningful evaluation of memory size will be possible only if the operating system had the chance to monitor typical usage of memory within a certain time interval. Perform the following steps to let TinkerTool System evaluate the memory usage statistics:
The current statistical readings will now appear in the upper box, the evaluation in the lower box Results. An evaluation is possible only after the system has been switched on for at least 2 hours.
The time of operation of Mac OS X in which the statistical data could be collected is shown in the last line of the upper box. You have to decide for yourself if the computer has been used in a “typical” way in this period. In case the usage was more untypical, e.g. because you have used more applications simultaneously than normal, or because you have worked on an unusual “giant” document that has consumed an extraordinary amount of memory, the results will not be meaningful.
In case you decide that usage of the computer has not been typical enough to allow a meaningful assessment, perform the following steps:
The upper box lists selected data from the memory statistics maintained by Mac OS X:
The box Results shows the current evaluation based on the statistics shown in the upper box. The assessment contains a textual explanation and a short overall result like “good” which is additionally being represented by the image of a traffic light. The program differentiates between the following results:
The program Finder typically used in Mac OS X to work with files and folders is affected by serious flaws in specific versions that can result in unexpected problems when copying data:
Whether these problems occur will depend on the version of Finder you are using, and on the question between which file system types you are copying data. File system type means the format of a disk or disk partition, or the transfer protocol being used when accessing a file server in the network, respectively. The Finder behaves differently when copying between two HFS hard drives, for example, or between an HFS disk and a memory stick formatted using the FAT standard of Windows, or when copying from an AppleShare file server to an HFS disk.
If you want to achieve certain knowledge whether there is the possible danger that the Finder could damage data when copying files, or might terminate the copy operation unexpectedly, you can let TinkerTool System check two given disks against your version of the Finder. TinkerTool System can control the Finder remotely to test which operations run as expected and which do not. To perform the check, you only have to specify two folders between which test files should be copied.
To run the tests, TinkerTool System needs less than 200 kiB on both disks. All files written during the check will be erased automatically after the tests have been completed.
Perform the following steps to test the Finder:
The button can only be pressed if the aforementioned prerequisites are fulfilled for the two folders. The box Results will show you in advance whether the test can be performed, or if there is a possible problem with the selection of folders.
TinkerTool System automatically tests the copy operations in both directions, i.e. copying from folder 1 to 2, and from 2 to 1. The order of the two folders doesn’t play any role for this reason. Because TinkerTool System is controlling the Finder remotely, you might hear the sound effects the Finder uses for copy operations in rapid succession during the test.
After all tests have been completed, the box Results will show how the respective version of the Finder has behaved in regard to the file systems specified. A test that succeeded without problems will be displayed by a check mark with green background, a test which has failed is shown by a cross marked red. A big icon on the right side will summarize the overall result.
Please note that TinkerTool System is only testing whether the Finder is working as expected. The application cannot repair any defects it might have detected in the Finder.
If one of the tests is failing when you had selected two HFS disks for the copy operation, you unfortunately have to expect that Time Machine also won’t work correctly. Because the Finder is an indirect part of some copy operations performed by Time Machine, backing up or restoring data can also lead to corruption of copied files.
If your computer contains one or more optical disk drives with writing capabilities, you can use TinkerTool System to retrieve detail information about inserted disk media, like CDs, DVDs, or Blu-Ray Discs. This feature is helpful to find out the actual manufacturer of a storage medium, or to get information about the recording format of a disk. Depending on the type of medium and its storage format, the amount of data you can retrieve will be very different. With appropriate media, TinkerTool System may include the following detail information in the results:
Not only the type of storage media, but also the question if data has already been recorded on the disk will determine which information items will be retrieved and which not.
To inspect optical disk media, perform the following steps:
The analysis will be shown in the box Results after a few seconds.
Note the difference between the items Media Type and Media Behavior: If you have recorded a digital video on a disk of type DVD+R and have correctly finalized this recording session, the physical type of medium will be DVD+R, but the disk will finally behave like a DVD-ROM.
In case you are not using the typical “Superdrives” by Apple, the application will only support optical drives which can both read and write disks.