OS X Yosemite: If your Mac runs slowly
If you find your Mac is running slowly, there are a number of potential causes that you can check.
An app you’re using may require more memory than your computer has easily available. To see how much memory your computer has, choose Apple menu > About This Mac, then click Memory. See the help that came with the app to see its system requirements.
To find out how to increase your computer’s memory, choose Apple menu > About This Mac, click Memory, then click Memory Upgrade Instructions in the lower-left corner.
documentation that came with the app to its system requirements.-
To see what processor your computer has, choose Apple menu > About This Mac, then click Overview.
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To see what graphics card your computer has, choose Apple menu > About This Mac, then click Displays. The name of the graphics card in your computer is displayed in the middle of the window.
Your computer’s startup disk may not have enough free disk space. To make disk space available, move files to another disk, then delete files you no longer need on the startup disk.
Quit any apps you’re not using.
If you have problems with your disk, use Disk Utility to verify and try and fix any issues.
Use Activity Monitor to see if a particular app or activity is making a large demand on your Mac.