Do you have a Mac that is gaining a few years on it and is not performing the same as you remember when you first bought it? While you might not be able to pinpoint it, you might simply notice programs take longer to launch, or you now have to wait a few extra moments for other tasks to complete.
Sometimes such slowdowns are caused by errors such as damage to the filesystem. Alternatively, over time as program and the Mac OS evolve, they will demand more out of a system, making it progressively difficult for an older system to keep up.
In many cases an older systems will have the horsepower to run the software you have installed, but are simply limited in capability by some of the configurable options that were available when you configured the system for purchase, primarily the amount of RAM and the hard drive type and size.
Your Mac’s RAM
One of the biggest factors determining the speed of a system is going to be the amount of RAM installed, so if your older Mac is sluggish then you might first take a look at your RAM usage and see if you can accommodate it. Open the Activity Monitor utility and check the Memory section to see if you are regularly using the full capabilities of your installed RAM.
In OS X before Mavericks, locate the pie chart in the System Memory section at the bottom of the Activity Monitor window under normal working conditions, and see if the combined blue and green sections of the chart are relatively small (about a quarter of the chart, or smaller).
Additionally, check the Page Outs, and Swap Used status listed next to the pie chart. If the Page Outs are high and regularly counting up, and the Swap Used is regularly in the hundreds of megabytes or gigabytes in size, then the system is regularly writing memory contents to the hard drive to free up physical RAM for other purposes.
In OS X Mavericks and later, locate the Memory Pressure chart in this same area of Activity Monitor, and see if the pressure level is small (about a third or less of the chart’s area, and green in color).
Unfortunately with the introduction of the Memory Pressure concept in Mavericks, Apple did away with its measurement of Page Outs; however, Swap Used is still there. In addition, you can check the “Compressed” level to see how much memory is being compressed by the system. If the compressed memory level is regularly about 20% of the amount of Physical Memory installed, then you should consider upgrading your RAM or reducing the number of programs you have open at any one time.
In these cases, you can either look into purchasing more RAM, or changing your workflow to decrease the amount of RAM being used. These days 4GB-8GB of RAM is an average to have (with 8-16GB being necessary for more demanding tasks), which contrasts with only a few years ago where you could get away with using 2-4GB of RAM.
Your Mac’s hard drive
A second component of your Mac that may contribute to slowdowns is its hard drive, especially in instances where you are low on memory and the system writes memory contents to disk (the Swap Used and Page Out statistics mentioned above). RAM can be accessed and read at gigabytes per second, whereas mechanical hard drives are accessed at around 20-80MB per second, resulting in a major bottleneck for program functions. If the hard drive is further limited by filesystem damage, or by simply being full, then you may see an even greater degradation in performance.
Because of these factors, there are several approaches you can take to open this bottleneck:
Regularly check your hard drive for errors
Open Disk Utility every month or two and then select your hard drive in its sidebar, followed by clicking the Verify Disk button in the First Aid tab. If any errors show up when you do this, reboot into Recovery mode and then use Disk Utility there to fix the errors.
Keep at least 5-10% of your hard drive free
Since your system will use the hard drive as temporary storage for unused RAM contents, it is best to keep at least a small amount of it free by removing unused programs and data, or moving them to an external hard drive.
Upgrade your hard drive to an SSD
There is no way to prevent OS X from using the hard disk for memory management, but you can help the system by providing a faster storage medium to work with than the conventional hard drive, by replacing it with an SSD (even a cheaper one that is a generation or two old). Not only will this help speed up memory management routines, but will also help in the loading of the system, applications, and data.
You can consult with sites like iFixIt.com for guides on how to access and upgrade the hard drive on your specific Mac model.
Your OS and software
Finally, if you are using OS X 10.7 or 10.8 and your system will run OS X Mavericks, then consider upgrading it, especially if your Mac has around 4-8GB of RAM. While it may seem logical to keep an older version of OS X since newer versions may demand more out of your Mac, some of the ways newer versions of OS X will handle memory management and background processes may in fact show an increase in performance. For example, memory compression in OS X Mavericks will help make more RAM available to active programs, and its ability to freeze hidden applications that are not being used will allow the CPU to work on more relevant tasks.
If you upgrade your OS, the same goes for any programs you use, especially if you would like to ensure they work best with the new operating system’s services and features.
Beyond these three options, you can look into uninstalling programs you do not use (especially if they provide active system-monitoring or scanning features), and removing login items from your account to prevent unnecessary programs from opening when you log into your Mac.
Lastly, sometimes there might simply be a collection of problems with your account’s configuration that are numerous enough to make troubleshooting a frustration. To test this, try simply creating a new account and then logging into it, to see if the problems persist. If not, then consider migrating to the new account permanently and using it from now on.