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The Best Way to Speed up a Slow iMac 2012 to 2019 Computer

Why is my iMac Computer so Slow, and what is the best way to speed up a slow iMac Computer without an expensive iMac computer repair cost?

Keith Thomas Apple Support Specialist Logo

The best way to speed up a slow iMac computer that has become slow, or has suddenly become slow, and you need a way of getting much better speed and performance, and you do not want to have to get the iMac computer repaired, or Apple will not longer service your Slow iMac Computer, then one of the very best ways to help speed up a slow iMac 2012 to 2019 computer is to install Mac OS to an external SSD Flash Storage volume. By using an external SSD Flash Storage volume the iMac Write and Read Speeds are much faster if the internal storage volume has a degraded performance.

Find out the Best Way to Speed up a Slow iMac 2012 to 2019 iMac Computer that has become slow or very slow, by creating an external SSD for iMac boot drive.

The Best way to Speed up a Slow iMac 2012 to iMac 2019 Computer.

The Best Way to Speed up a Slow iMac 2012 to iMac 2019 Computer that has become slow, and with a iMac 2012 to iMac 2017, Apple will no longer offer a iMac SSD Upgrade service to replace the internal storage volume that has become slow or very slow.

  • Best external hard drive for iMac.
  • External SSD for iMac.
  • How to speed up slow iMac.
  • iMac External SSD 1Tb.
  • iMac External SSD Boot Drive.
  • iMac External SSD bootable Drive.

The Apple iMac 21.5-inch desktop computer that Apple manufactured from 2012 to 2019 often had a 1TB SATA Macintosh Hard Disk Storage volume, and it is well known that the performance of an iMac 21.5 desktop computer model with a SATA 1Tb storage volume can have a slow performance, causing the Apple iMac computer to become slow or simply very slow due to the write and read speeds of a degraded 1Tb Macintosh HD mechanical hard disk drive.

iMac performance information that you need to know.

The very best way to get performance from any Apple Mac computer is for the Apple Mac computer to use SSD Flash storage internally, however with the Apple iMac 21.5-inch 2012 models to iMac 2015, and iMac 2016 models are no longer serviced by Apple or an Apple Authorised service provider, which means that for a iMac 2012 to iMac 2016 models can only use the option of an external SSD boot drive to speed up a slow iMac desktop computer.

For Apple iMac computers that are 2017 or newer to 2019 Apple will service these iMac models with a iMac SSD upgrade service for iMacs that have either a SATA Macintosh HD or a Apple Fusion Drive.

Use an External SSD Flash Storage as a iMac Bootable Drive to get the very best possible performance for a iMac 2012 to iMac 2019 comput4r, without having to get the internal storage volume replaced with a internal SSD storage volume.

Prices for external flash SSD storage is now cheap and very cost effective, as SSD flash storage volumes are more popular.

And are much more reliable and cheaper to buy, crucial, western digital, are two of the main manufactures of external SSD flash storage devices that work well on the Apple iMac computer as an iMac external SSD boot drive.

Best external hard drive for iMac.

Their is no Best external hard drive for iMac as the iMac has a USB port that is limited in speed, an external SSD Flash storage volume, from any well known and braded vendor, will work at the same or at a near similar speed and performance.

How to use iMac External SSD Boot Drive to make a iMac 2012 to iMac 2019 model much faster to use.

How to create an external bootable macOS SSD boot Drive for fast iMac performance.

Total Time: 12 hours

Buy or purchase the iMac external SSD boot Drive.

Sabrent external NVMe USB-C with 1Tb WD storage module

Buy or purchase an external SSD flash storage drive which is the same or higher capacity as your Apple iMac computer.

If you use much less storage space then 1Tb then a 500Gb flash storage can work, but the price for a 500Tb is very close to a 1Tb one. Buy another one if you need to back up the iMac computer to Apple Time Machine if you do not have a current iMac Apple Time Machine backup.

Make an Apple Time Machine backup of the Apple iMac desktop comptuer.

Apple Time Machine Backup

Having an Apple iMac Time Machine backup is critical for an older Apple iMac computer, and it is a step that need to be done.

1. Connect a external USB (USB-A) external storage volume to the Apple iMac computer and open Apple Time Machine from the System Preferences Panel, and choose Time Machine.
2. Use the Select Disk button and then choose the external USB storage volume, if prompted then Erase the Storage volume as prompted by Apple Time Machine.
– If this does not work than use the Apple Disk Utility software tool found in the Applications Folder and in the Utilities Folder to Erase the external SSD to MacOS Extended journaled format with a GUID partition scheme.
3. Try step 2 again once the external storage volume has been Erased (Formatted to Extended Journalled format, GUID.
4. Wait until the Apple Time Machine has completed.

Prepare an iMac External SSD boot drive storage volume.

Apple Disk Utility on macOS Catalina showing containers

Use the Apple Disk Utility to Erase (Format the iMac external SSD boot drive storage volume)
– For macOS High Sierra or earlier macOS use Extended Journalled GUID.
– For macOS Catalina or newer macOS versions use APFS and GUID.
– Use the View Menu and make sure that you Highlight an External Storage Volume! The name will depend of the manufacturer of the external storage volume.

Restart the Apple iMac Computer.

Use the Apple Menu Item Restart to restart the Apple iMac computer and then hold down 2 Keys, the Command Key, and the R Key, and keep these two keys held down.
The Apple iMac computer should startup to the macOS Recovery Console.

Choose the option of either Restore from Time Machine or the option to re-install macOS.

The best way to migrate from a Macintosh HD SATA Storage volume, to an external SSD storage volume, is to restore the Apple iMac computer from a previous Apple Time Machine backup. If you need to create an iMac external boot drive without using a Apple Time Machine backup then choose re-install macOS, and follow step 4.

1. Select Restore from Apple Time Machine from the macOS recovery console.
2. Choose the date and time of the Apple Time Machine backup, then click next or continue.
3. You will be asked the destination of where to Restore the Apple Time Machine backup to.
4. Choose the external SSD flash storage volume as the destination.
5. Click on next or continue and follow the on-screen instructions.

macOS will be installed to the external storage volume.

The Apple iMac computer may restart a few times, to complete the process. Once macOS is up and running if you choose re-install macOS then the setup will be the same as buying or purchasing a new Apple iMac computer. If Apple Time Machine is used then you might need to enter the iMac computer account password or create a new iMac computer account password to complete the setup.

Apple iMac 2012 showing Black Magic Speed Disk Check on internal 1TB SATA vs External iMac external SSD boot drive.

You can see that the image picture on the right is showing a much faster Write and Read Speed in MB/s in fact the MB/s actually reads 400 MB/s for write and 400 MB/s on Read. the Write and Read speeds are critical to make an Apple iMac 2012 or newer iMac to 2019 way faster to bypass the slow or very slow internal Apple 1TB SATA 1TB storage volume which in fact has a poor rotational speed of 5400-rpm even a 33% 7200-rpm 1TB SATA Macintosh HD is slow vs a iMac external SSD boot drive.

How do I make an external SSD bootable for Mac?

External NVMe Enclosure with Western Digital NVMe

By using the Mac OS Recovery Console and by formatting an External SSD storage volume to the right format, making an External SSD Bootable SSD for Mac can be rather simple to do if the correct steps are taken

1. Start the Apple Mac Computer by either holding down the Power Button on newer Apple Mac Computers, or use Command R on Intel Apple Mac Computers.
2. Connect an External SSD Storage Volume to one of the USB Ports on the Apple Mac Computer, for an Intel iMac use a USB A to USB C Adaptor for an External SSD storage volume that has a USB C port.
3. From the Mac OS Recovery Console, the Apple Disk Utility Tool, to Erase the External SSD, this will Erase all of the Data on the SSD and this cannot be recovered.
4. Use the right format for the Mac OS Operating System Software for newer versions of Mac OS use APFS, and for Older Mac OS versions use Mac OS Extended Journaled. Mac OS Catalina and newer Mac OS needs to be APFS, GUID format.
5. Once the External SSD has been formatted, then Quit the Apple Disk Utility.
6. Now use the MacOS Reinstall option and Reinstall Mac OS, and choose the External SSD storage volume to Reinstall Mac OS.
7. The Mac OS operating system will now install to the External SSD Bootable storage volume.
8. The computer will restart a few times, and once Mac OS has been installed the Mac OS startup volume will be from the External SSD Bootable Storage Volume.
9. The Alt Key on Intel Mac OS Computers on start up will show a Mac OS Start Up Menu, you can choose the Internal Macintosh HD or the External Bootable SSD if this is connected to the Apple Mac Computer. Mac OS will start up to the External SSD if the External SSD storage drive is connected to the computer, without having to use the Alt Key.

Apple iMac computers that have a 1TB SATA Macintosh HD internal storage volume can be slow, so an iMac external SSD boot drive can be used to either install macOS or to restore an iMac from Apple Time Machine backup to an macOS Extended Journaled or to a APFS format, depending on the macOS operating system software version. a iMac 2012 model will support APFS for macOS Catalina, and macOS Extended Journaled for macOS High Sierra. The Write and Read speed are much faster for an iMac 2012 to iMac 2019 models that use an iMac external SSD boot drive.

How can I get help with a slow iMac Computer?

Keith Thomas can help with a Slow iMac computer by iMac Telephone Support Service. With help with setting up an external SSD bootable storage volume, which can help speed up a slow iMac desktop pc computer.

The best way to speed up a iMac computer that has an internal SATA storage volume is to create a iMac external SSD boot drive as a workaround to getting an iMac SSD upgrade.

Will Apple upgrade my iMac computer with a SSD Flash storage volume?

Apple for a short period of time offer in 2023, an iMac 2017 SSD Flash Storage upgrade service, and an iMac 2019 SSD Flash Storage upgrade. For iMacs that are 2012 to 2016 models Apple will not offer an iMac SSD upgrade service, a work around is to create an iMac external SSD boot drive.

Can you use an External SSD on iMac?

Crucial P5 M2 2280 in external USB-C enclosure

Yes. For iMac 2012 to iMac 2019 Computers, using an External SSD on iMac can give a much better performance than using the Internal iMac Macintosh HD Storage Volume, as an External SSD on iMac 2012 to 2019 will be about 400 Mb/s Write and 400 Mb/s Read Speeds which is often much faster than the original iMac Macintosh HD which Mb/s is no faster than 300 Mb/s and usually much slower at 60 Mb/s to 100 Mb/s for a 1Tb 5400 SATA Macintosh HD

Can you run an iMac off an External Hard Drive?

Sabrent external NVMe USB-C with 1Tb WD storage module

Yes. Mac OS Supports Booting an iMac Computer from an External Hard Drive, but for a Mechanical Storage Volume, the speed will be slow, for the best performance use an External SSD Storage Volume. for newer iMac M1, and iMac M3 computers, the Internal Storage volume is much faster, so using an External Hard Drive, or an External SSD gives a slower performance, but for an iMac 256Gb Model and more useable storage volume space is needed then an External SSD 1Tb, 2Tb, 4Tb, 8Tb storage volume will give 800 Mb/s to 1050 Mb/s Write and Read speeds, which is very fast for a Home or for a Work iMac M1, iMac M3 computer that has a 256Gb or a 512Gb Storage volume and you need to store more information on the computer.

How fast is external SSD for iMac?

DiskSpeedTest iMac 2012 SSD

An External SSD for iMac Speed depends on the iMac Model, a iMac 2012 computer with a USB 3.0 port with an External SSD for iMac will give about 400Mb/s Write and 400Mb/s Read Speed. A iMac M1 computer with a USB-C External SSD for iMac M1, will give about 800 Mb/s and a iMac M1, iMac M3 computer with a Thunderbolt External SSD will give even more Mb/s Read and Write Speeds.

Can I leave an external SSD plugged in Mac?


What is the best format for SSD on Mac?