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Sudden iMAC slowdown

My 2017 27" 3.4 GHz Quad-Core Intel Core i5 iMac with 64 GB 2400 MHz DDR4 and a 2TB HD has suddenly started pausing when I open all apps or files, with frequent spinning color wheels. Using Activity Monitor I see no correlation between when this happens and %CPU use by any app (i.e., it doesn't just happen when there's high use). And I have 1.5TB free on the HD and there has never been any "memory pressure" according the Activity Monitor. I've run Apple's hardware diagnostics, which say the machine is fine. What could this be?

iMac 27″ 5K

Posted on Aug 26, 2023 11:49 AM

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7 replies

Aug 26, 2023 1:03 PM in response to Japple-23

Apple's diagnostics are not a very good tool at all. Your HD may be failing and Apple Diagnotics may have missed that. If you want to check the health of your HD, then download the free version of DriveDX and test your drive. If ANY errors appear that means the HD is failing and must be replaced. I also recommend that you do the following:


It will help us get a good idea of what is causing your problem if you provide a report of your system, that way we do not have to play 20 questions with you. The report we are requesting does NOT provide any personal information and is extremely safe to use. Please navigate to www.Etrecheck.com and download the free version of EtreCheck. Once you have you downloaded the app and installed it, please run the report and save it. This report will help us get a good idea what has been installed on your system and help us be able to diagnose what may be wrong.


When you have your report, you can attach it when you reply to this message and we can then review it and help you determine what is needed to get your system running well again. 


For instructions on how to download your EtreCheck report and attach it to your reply to this message please click How to use the Add Text Feature When Post… - Apple Community It is helpful to us if you download the report to your Desktop.



Aug 26, 2023 4:23 PM in response to Japple-23

You've installed two very nasty apps, CleanMyMac and Bitdefender Virus Scanner which most experience users here consider akin to malware. The Diagnostics at the end of the report confirm that these are the two most damaging to system performance.


First, there is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This documents describe what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community and Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support.  


There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   


Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.


There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is designed solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  


That being said uninstall those two apps according to the developer's insturtios. You can check to see if you've removed all of the supporting files by downloading and running the shareware app Find Any File to search for any files with the application's or the developer's name in the file name.  For the two apps indicated you'd do the following search(es): 


1 - Name contains cleanmymac

2 - Name contains macpaw

3 - Name contains bit defender


Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.


FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  


If you get warnings that the file can't be deleted because it is in use or used by another app boot into Safe Mode according to How to use safe mode on your Mac and delete from there.


Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.


Aug 28, 2023 12:42 PM in response to Japple-23

Nope your Hard Drive is failing and must be replaced. Please take it to your local Apple Authorized Service Provider and ask them to upgrade to an external SSD which will save you a LOT of money. If you want to do it yourself here is a link to instructions:


Use an external SSD as your startup disk … - Apple Community


You can trust the report in DriveDX however you cannot trust the report in Apple diagnostics. Please handle this ASAP, based on your DriveDX report the internal drive could fail at any time!!!!!!!!

Aug 28, 2023 12:46 PM in response to Japple-23

I recommend drives from OWC (MacSales.com) as they have proven reliability, excellent customer support and warranties.  OWC is considered the premier 3rd party hardware supplier for Macs by most of the experienced users here.


Consider one of these depending on your budget and needs: 


OWC Envoy Pro FX Thunderbolt 3 + USB-C Portable NVMe SSD**

OWC Envoy Pro SX Rugged Portable NVMe SSD with Thunderbolt/USB4

OWC Envoy Pro Elektron USB-C portable NVMe SSD

Envoy Pro EX with USB-C or USB 3 


For your particular Mac model contact OWC's customer support and get their recommendation for the SSD model that would best suit your iMac model, work requirements and budget.  They may have additional models other than those I've shown above.


Sudden iMAC slowdown

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