When your computer is running a bit slowly, how can you tell if getting more memory will help? The short answer is that if you have little or no ‘free memory’ or if your ‘page-out’ count is high, then you need more RAM. Here’s how to check those two things on any Macintosh running OS X.
- Go to your Applications/Utilities folder. (Click on your desktop so that the finder is active then hold down Apple-Shift-U, this will open your ‘utilities folder.)
- Open ‘Activity Monitor’ – it will probably be the top-most application in the Utilities Folder.
- Press Apple-1 to make sure that the main window of Utility Monitor is open.
- Click on the ‘System Memory’ tab at the bottom of the window. This will display a little pie graph of how much memory you are currently using. It will look something like this:
There are two important items to take note of ‘Free:’ and ‘Page outs:’
Free tells you how much free memory you currently have available to use – the higher the better. If you have no free memory you should get more RAM.
A Page out means your computer has run out of memory and had to use some of the Hard Disk instead of RAM. (This is the equivalent of your brain being too full so you have to write your thoughts down on paper to free up some headspace) This DRAMATICALLY slows down your computer.
To quote from Apple:
Moving data from physical memory to disk is called paging out (or swapping out); moving data from disk to physical memory is called paging in (or swapping in)… Extended periods of paging activity reduce performance significantly; such activity is sometimes called disk thrashing.
Tip: Page outs occur when your Mac has to write information from RAM to the hard drive (because RAM is full). Adding more RAM may reduce page outs.
In OSX Leopard rather than giving a ‘count’ of page in and page outs, it gives a size in GB of the amount of RAM that has been paged in or out. The numbers are smaller but the same principals apply.
In OSX Lion there is a new entry called ‘Swap Used’. (See the last picture above). This is a count of how much Disk Space your computer is using as RAM and it’s a good rough estimate of the minimum amount of extra RAM you need. Eg If your Swap used is 4G then get AT LEAST 4G more RAM.
Where to buy more RAM.
If you do need more memory I recommend buying it from Crucial. They have good prices and reliable RAM. I’m in Australia and it usually arrives in about a week. They have a great memory lookup tool for all Apple Computers where you choose your model and it shows you exactly what memory you need. The memory chooser tool looks like this:
First choose ‘Apple’ where it says ‘Choose Manufacturer’
Secondly select your mac when it says ‘select product line’ (e.g. iMac or Macbook etc)
Finally select the exact model (e.g. Early 2011 i7 27″ iMac”)
It will then show you the options you can buy.
Note (Jan 2013): I have signed up as a Crucial affiliate partner.