I just restored my old Late 2009 27" Quad core iMac, from Time Machine to a Late 2012 21" i5 iMac, and at certain points it is very slow and laggy. For example when I try to open Photoshop, or just randomly when I am on the browsing the Web using Google Chrome.

Nothing seems to be using too much of the CPU or the RAM, but maybe I need to do some kind of system clean. I already installed the newest OS which seems to have helped.

Can anyone please let me know what might be the best solution, or general steps which should be taken in this case.

  • Welcome to Ask Difference :) Not sure but slow hard drive could be the culprit here. 2012 teardrop design iMac feature slower 5400 RPM hard drives unlike the earlier ones featuring 7200 RPM drives. The perceived slowness could be causing due to heavy disk activity.
    – Nimesh Neema
    Apr 15, 2019 at 9:09
  • Thank you. Could you tell me what is the best way to test if it is the hard drive? Apr 16, 2019 at 6:46
  • Determine the disk type installed in your iMac, which should be easy to do based on whether it's a standard config or customized one. Check if it has Fusion drive or not. You can also use a disk speed checking tool such as Blackmagic Disk Speed Test to determine disk read/write speeds. (No affiliation to the developer, it's a popular tool).
    – Nimesh Neema
    Apr 16, 2019 at 6:50
  • I have added the information of both below. It looks like I might actually have an HDD? If so, should I get an external SSD? Write54 Read41 Available: 563,34 GB (563.338.051.584 bytes) Capacity: 1 TB (999.995.129.856 bytes) Mount Point: / File System: APFS Writable: Yes Ignore Ownership: No BSD Name: disk1s1 Volume UUID: BEA658E9-BCB1-3254-997C-7606832B692E Physical Drive: Device Name: APPLE HDD HTS541010A9E662 Media Name: AppleAPFSMedia Medium Type: Rotational Protocol: SATA Internal: Yes Partition Map Type: Unknown SMART Status: Verified Apr 16, 2019 at 10:07

1 Answer 1


It can take a while for a Mac to reindex all your files after an OS upgrade. Leave it powered on and mostly idle for a day or two, especially if your disk is nearly full. That will give it time to complete its background tasks.

  • It was actually slow even before the update. For example when I click on photoshop, the app in the dashboard hops much longer and takes more time to open than usual. Although the mac isn't needing much power for these things, every click is somehow slow. Is there any way I can test to find out the problem? Apr 16, 2019 at 6:17

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