After RAM upgrade, my iMac's system booting process has become too slow

Thank you for the report

From my experience and this is subjective and based upon what I have seen time and time again

This will include CleanMyMac

I will be brief with Capital Letters >> CleanMyMac

Part 1 of 2

Once this type of software becomes embedded on / in the computer

Start Over from Scratch 

You can spend hours or days hunting down all the bits and pieces of this software and never really get it all off the computer 

For Apple Silicon computer >> Use Disk Utility to erase a Mac with Apple silicon.

For Apple Intel computers >>   Use Disk Utility to erase an Intel-based Mac followed by How to reinstall macOS

Part 2 of 2

Specific to CleanMyMac aka “ BrickMyMac “

To put the CleanMyMac in context and the damages it may have or has already done.

This application can or will Muck Up your User Account ( Home Folder ) of this machine.

It does not touch the Operating System itself unless you consider your User Account ( Home Folder ) as part of the Operating System

Then in that specific context - it has Mucked Up the Operating  System 

In which case, the Operating System is hosed

If going this route - I suggest Not using Startup Assist to migrate everything back.

This will probably Re-Introduce (CleanMyMac aka BrickMyMac ) back into the Operating System 

EDITED by me

Does the System Recognize the additional RAM

Finder >> Utilities >> System Information >> Memory

If it does see the additional RAM

The is probably some Other issue(s) preventing the machine to performing better than is is now

Download the Application Etrecheck  ( External Link ) directly from the Developer.

The Application is Not a " Silver Bullet "  and is  only a tool to examine the Hardware / Software used on this computer 

This is a Diagnostic Tool that makes no changes to the computer Hardware / Software used on this computer 

The application is free or paid from added features. 

The Report will Not Reveal Any Personal Information. 

Post back the Full Report - copy and paste - >>>> using the Additional Text Icon ( 3rd Icon to last ) <<<<

I just did a quick review of the report and I strongly suggest that you completely remove CleanMyMac. Then use your Mac for awhile to see if the boot up process improves.

Additionally, overall slow performance could indicate a failing HDD. Fusion drives tend to have this issue. For that I suggest that you download and run DriveDx and post the resultant report if you need assistance with interpreting its results.

Usually, reports of slow iMac are due to old-school storage, but not in your case This:

Performance:

System Load: 1.65 (1 min ago) 1.34 (5 min ago) 1.28 (15 min ago)

Nominal I/O usage: 0.03 MB/s

File system: 24.08 seconds

Write speed: 866 MB/s

Read speed: 1468 MB/s

shows you have speeds within the nominal range for Apple's Fusion drive system, and the other metrics indicate a healthy drive. That should not feel slow.

What brand of RAM did you install? Intel Macs are picky about RAM, and "value RAM" too often creates odd problems. Most senior contributors here recommend only Crucial or OWC RAM.

Remove the "generic Flash disk" the report shows and try speed testing again. It's USB 2 and I'm starting to see USB 2 externals slow some newer Intel Macs.

Your Drive X test only examined the SSD component of your Fusion system. Fusion is a small fast SSD and a large convention rotational hard drive linked by software to act as one. Most commonly the mech drive is the problem but your Drive X report did not pick it up the mech.

⚠️⚠️ Reinstalling the OS is NOT a first-line troubleshooting feature and may well break your Fusion software link system, resulting in speeds you have to time with a calendar . I see too many Fusion Macs messed up by an ill-advised reinstall. Don't do that at this point!!!

ad0312 wrote:

Thank You. Sincerely appreciate your help.

How does one clean the system of ClanMyMac? Is there any effective tool?

I realised CleanMyMac was a pain after using it for a few years.

Thanks once again.

Regards,

AD

You are welcome

Effectively remove " BrickMyMac "

Please consider the earlier posting >> " Start Over from Scratch  "

Then and only then follow the advise from @ Tesserax

I feel the need to ask - is the RAM you bought spec'd as DDR4 PC4-21300 2666MHz? Because that is what your machine needs and there are similar sticks (e.g., PC4-25600 3200MHz) that could work, but not well due to bus clock incompatibilities.

The fact that your etrecheck report lists the RAM clock speed as 2667 instead of 2666 makes me wonder if the timing is not quite what the iMac is expecting.

If I were you I would reinstall the operating system that you have installed that should fix it.