What does mem­ory pres­sure ac­tu­ally mean?

Mac Format - - APPLE TALK -

Q I use a 2009, 27-inch iMac, with a 4GB mem­ory. It’s been rather slow since in­stalling Mav­er­icks. The 1TB hard drive was only 20% full, so I sus­pected mem­ory. Sure enough, Ac­tiv­ity Mon­i­tor showed that mem­ory used was usu­ally about 3.95GB of the 4GB avail­able, de­spite Mem­ory Pres­sure be­ing in the low green. I up­graded to 8GB and find that mem­ory used has gone up to around 7.95GB, with Mem­ory Pres­sure still a low green. Can you ex­plain please? An­drew Frost A When you open an ap­pli­ca­tion in OS X it’s loaded into free RAM. The other open apps are left in mem­ory, even if they aren’t be­ing used. Once you get to the point where there isn’t any free mem­ory left, the OS starts ac­tively man­ag­ing the mem­ory in use. Ini­tially it will re­quest that apps dump un­needed data and it com­presses the data in mem­ory pages that haven’t been ac­cessed for a while. When it’s do­ing this, the Mem­ory Pres­sure graph shows yel­low. If that isn’t enough, mem­ory pages will start get­ting swapped out to the disk and the graph changes to red. Un­less Ac­tiv­ity Mon­i­tor con­sis­tently shows Mem­ory Pres­sure in yel­low or red, adding more phys­i­cal RAM won’t help. On a six-year-old Mac, it’s more likely that the graph­ics chip and CPU are lag­ging be­hind the re­quire­ments of mod­ern apps. It’s also pos­si­ble dust has built up in­side. If your fans are nor­mally run­ning full blast, con­sider open­ing the case for some dust­ing.

Dust gets sucked into your iMac through the air in­takes, so be sure to give them a clean now and again.

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