You can make a difference in the Apple Support Community!

When you sign up with your Apple Account, you can provide valuable feedback to other community members by upvoting helpful replies and User Tips.

Looks like no one’s replied in a while. To start the conversation again, simply ask a new question.

Will downgrading Big Sur improve my computers performance?

Will downgrading macOS Big Sur Improve my computer's performance?

I've recently got an iMac (21.5-inch, Late 2015). When I bought it, Big Sur was freshly installed, my problem is the computer is running very slow.


The main problem seems to be a strain on the ram (8GB) it's very slow to start up and freezes a lot, even when doing simple tasks such as opening system preferences or using spotlight search, right now with just safari running 6GB of the 8GB of ram available are being used.


I'm not sure wether to downgrade my OS to Catalina, as from what I've read this OS isn't as RAM-hungry.


Is this a good idea? I like the aesthetics of Big Sur, but most importantly I use handoff between my 2018 MacBook Air daily, and I'm not sure if downgrading would affect this.


Additionally, I'm aware that there is a new OS coming out soon, which is compatible with my iMac, seems that It would be a silly question but is it possible that this OS might improve performance? Or is it a case of the older OS the better?


Thanks in advance, this will really help me out.

iMac 21.5″, macOS 11.6

Posted on Oct 16, 2021 11:54 AM

Reply
Question marked as Top-ranking reply

Posted on Oct 16, 2021 2:31 PM

Know that the model iMac that you have was the slowest iMac offered by Apple at the time of purchase: 8 GB RAM and a 5400 rpm hard drive. There's nothing you can do about the RAM but P. Phillips has given you an good solution to fixing the slow boot drive.


Also, 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 user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.  


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 desshoigned solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  


So uninstall Avast Cleanup Premium according to the developer's instructions.


I also noted that you haven't rebooting in 2 days. You should not let it go beyond about 2 days without rebooting. That clears out temp system and applications cache and swap files and will help in system/application performance.


Similar questions

11 replies
Question marked as Top-ranking reply

Oct 16, 2021 2:31 PM in response to eccletom

Know that the model iMac that you have was the slowest iMac offered by Apple at the time of purchase: 8 GB RAM and a 5400 rpm hard drive. There's nothing you can do about the RAM but P. Phillips has given you an good solution to fixing the slow boot drive.


Also, 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 user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.  


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 desshoigned solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  


So uninstall Avast Cleanup Premium according to the developer's instructions.


I also noted that you haven't rebooting in 2 days. You should not let it go beyond about 2 days without rebooting. That clears out temp system and applications cache and swap files and will help in system/application performance.


Oct 16, 2021 3:46 PM in response to eccletom

eccletom wrote:

Will downgrading the system OS improve the speed without the need to boot off an external SSD?

That is a Good Question.


In reality, whether running Big Sur or Catalina, the same issue will remain - the 5400 RPM Mechanical Drive. That one thing is the bottle-neck no matter what older version is installed.


Use the External SSD will allow a few more year usage on this 6 year old machine.



Oct 16, 2021 12:04 PM in response to eccletom

You need to determine why your computer is running slow. Post an etrecheck report so that we can see what may be contributing to the performance issue.

With respect to using RAM (6GB of 8GB), of what value is unused RAM? Unused RAM is wasted RAM. Why pay for 8GB RAM if you don't want the computer to use 8GB RAM?

Post the etrecheck report.


Oct 16, 2021 1:43 PM in response to eccletom

The Biggest Culprit is disk0 - APPLE HDD ST1000LM024 1.00 TB (Mechanical - 5400 RPM) and will always spin too slow to effect the performance desired.


Possible solution is get a reliable external SSD Drive with USB and install the OS to the external drive. Then, in System Preferences >> Startup Disk, make the external drive the startup disk by default OR use the Option key to bring up the Boot Manager and choose external drive

Will downgrading Big Sur improve my computers performance?

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.