iMac slows down after Big Sur installing

HOPE

Just wanted to add to this thread and say there is hope, because I thought there was going to be none after I installed Big Sur and waited for days.

I installed Big Sur (v 11.5) a few days ago... install took a few hours and then my system slowed to an absolute dead crawl. Pushing one key on the keyboard would result in either nothing or multiple key entries... a patient and slow key press finally got me logged on to my user account (there's only one)... once there, my mouse would take ~2-3 seconds to respond, was jagged, laggy, overshot the destination - in other words, impossible to control, as if every system resource was maxed out... mouse clicks were super problematic, non-respondent and delayed... the system was almost unusable.

I read comments in this thread, saw that lots of others were experiencing similar problems... I told myself to wait a day or so to see if some background processes were still resolving... all the system resource apps (Activity Monitor, Sys Info, etc) showed almost no resource usage, which seemed strange, so I waited. For two days... nothing changed... sys was still bogged down...

Woke up this morning. Checked Reddit, saw someone mentioned to reset the Systems Management Controller (SMC) by powering down and unplugging for 15 seconds and then powering back up. Check here: https://support.apple.com/en-us/HT201295

I powered down, unplugged and then for added good measure, unplugged all of my external drives (someone had mentioned USB controller issues, too)... it worked like a charm and true to some other posters I've seen elsewhere - the system feels faster than it ever was...

HUGE sigh of relief...

My sys specs:

iMac (Retina 5K, 27-inch, Late 2015) Processor 4 GHz Quad-Core Intel Core i7 Memory 32 GB 1867 MHz DDR3 Graphics AMD Radeon R9 M395X 4 GB

Good luck! Hope it works for you, too.

System: MacBook Pro (16-inch, 2019), 64 GB RAM, Elgato Thunderbolt dock, Apple Pro Display XDR

Symptoms: Delayed text while typing, sometimes lost characters, major lag when changing volume or switching Desktops, Thunderbolt dock was often not recognized without connect/disconnect cycling, Sound settings (Speaker/Mic) not retained, Camera not connecting. Much of what you've read on the other 11 pages of this issue. Many restarts, Bluetooth resets and the like.

Prescription: Read JayBizzle's post above. Reset the SMC. See here: https://support.apple.com/en-us/HT201295

Result: MBP is back to running smoothly like in MacOS Catalina. Thanks JayBizzle.

I’m definitely gonna add to this!! So I purchased my 2019 27 inch iMac (16 gigs ram) in middle of 2020. I use it strictly for recording and mixing music. So there’s hardly any other apps that I’ll open besides Logic Pro x, or maybe watching Netflix and streaming services every now and then. it was working OK when I was using Catalina, but then … I downloaded Big Sur 11. And everything went down the toilet, it started stalling for five minutes before it would even turn on. And even when it did I noticed a HUGE Change in performance when it came to opening and using Applications. Including my recording software. This is a brand new computer keep in mind, that I paid very good money for. So of course I’m gunna complain. I called customer service about eight times for the same reasons and they could never give me a clear answer on what to do (understandable) not everyone has all the answers. So I ended up eventually taking it into my local Apple store with an appointment to get it looked at. All they could tell me was they’re going to wipe out the entire computer and erase everything and start from scratch. That was a “Apple Genius” saying that. Which I said was fine, they did that and the problem still preceded. I know it has something to do with the updates. My fear is they created these updates on assumption that everybody is switching to the Apple one chip and moving away from Intel. I feel like they geared these updates to cater only to their Apple one chipped computers. I could be wrong but a part of me feels like I’m absolutely right!! This is ridiculous we all paid a hefty penny for these computers and they’re already throwing them out the window it seems like. But lets hope they do something about this!

Clearly Apple has gone to the dark side with a nasty update. You know they know (if we could only get an Apple employee on the OS dev team to speak LOL). They made an update that's good for some models (and their profit margins), but destroyed perfectly good computers with a dirty move. I am furious with this I'm not buying another mac ever, because somewhere in the near future I'll face the same putrid ***** because of another lame thing they do for their profits. Windows/bootcamp are my future

Apple does not care ... there's no money in it.