iMac slows down after Big Sur installing

App & System Services Core OS macOS

Created Jun ’20

Replies 180

Boosts 0

Views 59k

Participants 169

Hello!
I downloaded the macOS Big Sur image on MacBook Pro, then installed, everything works fine.
I started downloading the macOS image on iMac, but at the end I constantly got a loading error. Then I install image on USB from MacBook and installed it on iMac. After installation, iMac began to slow down, for example, it opens a folder in a few seconds or or launches the browser in 10 seconds.
With what it can be connected?

iMac (Retina 4K, 21.5-inch, 2019)
Serial Number C02Z1085JWDX

Boost

Osang OP

Mar ’21

Same thing here, I updated my iMac 2017 from High Sierra to Big Sur and everything went slowwww as a snail. The boot time is terribly slow and I'm seeing frequent spinning wheel when I'm working with Adobe apps such as InDesign as the file name's appearance takes time to load. It's a mistake that I shouldn't upgraded my mac because everything's fine with my High Sierra, and the Big Sur should namely as a Big Mistake. Now I'm thinking of downgrading because I can't work because of the frequent lag. Well, gonna use my Windows PC to continue my work and thinking I'll just erase the Mac's drive and install back the High Sierra again.

Unlike Windows, Apple's frequent OS changes makes their recent Macs obsolete. Thanks Apple!

RM1Tampa OP

Mar ’21

I bought an external SSD for my 2017 iMac, found an easy to follow Youtube video and it has sped up everything on the Mac. Boot up times went from a couple minutes to around 20 seconds. Opening an app went from around 30 seconds to about 3 seconds. Everything on my mac now runs tremendously faster. It’s sad that my $1,100 machine was so slow but my $80 fix has made it enjoyable to use. I now love my machine and didnt have to open it up or take it to a repair person. Some places were quoting me $400-500 to open it up and add SSD internally but the $80 Samsung SSD took about an hour to install following the Youtube video and didn't compromise the iMac in any way. My family and I own iPhones, iPads, iWatch, an Apple TV and this was my first iMac. I was sad with the speed to say the least but next time I know to get the model with SSD.

chriscaro OP

Mar ’21

Upgraded my MacBook 12 2015. Now, it's completely unusable and super slow. Firevault is turned on. Subjectively, when I had Mojave installed, everything was 2-3 times faster. I regret my decision to upgrade... I did it only because I wanted to test new apps in App Store. *******.

chriscaro OP

Mar ’21

*******!

hyder OP

Apr ’21

SAME HERE! OH GOD ITS SUCH A RELIEF KNOWING YOU GUYS ALSO HAVE SAME PROBLEM LOL. Jokes apart! Bought Brand New iMAC 2019 4k Retina and its SO SLOW on BIG SUR!!!! Cannot code or use Xcode at all!! All the time BeachBall keeps on coming and loading! SO FRUSTRATING! I was thinking of throwing the imac away!

Please can anyone tell is there a fix to this problem??

Grimrian OP

Apr ’21

Lots of complaints over slow Big Sur upgrade - in this case iMac 27" 2017 24GB 3.4 GHz - impossible to use after upgrade installation on fusion drive, same if clean install on external thunderbolt SSD - had to revert to Catalina - no explanations yet?

Finchy70 OP

Apr ’21

I have iMac (Retina 5K, 27-inch, 2019) and since installing Big Sur my boot times have increased by at least 300%. For the first 5 minutes after boot my iMac is unresponsive and any attempt to start an app takes around 5 to 10 minutes. I rebuilt the fusion drive and performed a clean install of Big Sur and this made no difference. My iMac is less than a year old and is almost unusable.

My Activity Monitor shows my system at 90% idle so I have no idea what is causing the poor performance.

blah_deblah OP

Apr ’21

Very simple. Either macs are dogs and we've all been sold a bill of goods or we're all weenies cuz everyone knows nothing ever goes wrong with macs.

Alfy1974 OP

Apr ’21

This is ridiculous, but has anyone contacted some Apple technician to find out more or if will be soon another update to improve this abortion?

Wully-m OP

Apr ’21

Is there a definitive answer to this irritating issue of slowness (to the point of not being usable ) on Big Sur. I'm so angry that Apple are not fixing this and there is no communication that I've seen.

lazyzeroed OP

Apr ’21

Yeah i'm wondering too. Is Apple ever gonna address this? I won't upgrade to Big Sur until i'm sure it won't slow down my iMac again.

ysmnkssm470 OP

Apr ’21

I’m literally going insane with big sur:(((((((((

ATL_Jim OP

May ’21

What's the latest on this issue of Big Sur slowing down iMac Pro's? I'm running a late 2019 iMac Pro, 10 core, 64 GB RAM, Radeon Pro Vega 64X 16 GB, 1tb, still running Mojave. The "upgrade" to Catalina caused crashing, slowness and wasted time, so I rolled it back to Mojave and have not had any issues. Should I stay with Mojave or perform the upgrade to Big Sur? Thanks

mmerges OP

May ’21

The exact problem happened to me and is still an issue. I have a 2017 iMac 27 inch. 40GB ram and a Fusion 27 hard drive. I also have a 15 inch MacBook pro. I updated both of them on the same day to Big Sur. My laptop has no issues but my iMac takes almost 10 minutes to startup. It is May 6th and I have not found a fix yet. I re-installed Big sur but the same issue. I am going to try and go back but I fear that the Big Sur upgrade (ya right ) has messed with the fussion drive.

RobertAndrews OP

May ’21

Is there anyone who hasn't experienced this problem? Anyone for whom the upgrade has gone just fine?

Are there any particular circumstances in common with these experiences?
ie. Is Big Sur also horribly slow if you do a clean install?

I have an iMac 2015 and am considering upgrading, but not with thee reports.

pushka OP

May ’21

I'm sharing an iMac Late 2014 (the oldest computer that is said to work with Big Sur)

It was very slow so we fully wiped the computer and installed a fresh copy of Big Sur, and it was still very slow, laggy etc.

We left the computer on doing nothing for 2 days and now it's fully fast as it was before - there are 2 days of background update processes that the mac doesn't tell you about...

brerlappin OP

May ’21

Did the iMac Late 2014 have a fusion drive?

kimardenmiller OP

May ’21

Late 2015 iMac with fusion. Don't want to upgrade to Big Sur reading these reports. Anyone else see the issue go away in a few days as was the case for @pushka?

FScarfato OP

May ’21

Hi! I have an iMac27" late 2014 and after I installed Big Sur 11.4 my system with 32GB of RAM and this (shit!) Fusion drive system is come really really slow... until to 15/20 min to lanch an app!!! And I think with the next versione of macOS 12.x it will be definitly "dead" for Apple... so I decide to remove macOS at all and try to install Ubuntu or other GNU/Linux based distro. I am an Apple user from 1995 and this make my really un-happy... No good solution I have found to solve this issue, the only one seams to be just only change internal drive with a full SSD disk (pity this means 3/400 Euros...)

Hilmi21_zul OP

May ’21

I have 27” imac late 2014 i7 cuad qore turbo ram 32g with frigin fusion too. 3tb. The best part is only 128g is ssd. Balance is hdd.definitely not obsolete yet with fast moving tech. Just like cr7 n messi. Still relevant. anyway. Same prob. Mac os big sur slow. Apple consider our mac is vintage. My solution, i drop fusion. Keep the 128 ssd bought new 500g ssd. Partitioned. Then reformat to mac os catalina. This is the way! This is the way p/s convert hdd to externals. N set up NAS. Network attached storage. Wireless. But lagging when accessed

ChrisHeart OP

Jun ’21

SAME PROBLEM I have latest iMac 27-inch, 2020.. it has 1tb flash drive (ssd) and 64gb ram. It was lightning speed in everything, booting up took literarily 6 sec. on BIG SUR until the recent update 11.4 (20F71).. it's all slow now !!! I suspect this new update might benefit the new m1 chip and create some issues with current intel chip processors.. hope they will read this and fix it with another update.. Even if you factory reset the imac and install a clean Big Sur it will probably be downloaded with this new update..

paul darky OP

Jun ’21

Same problem. Recently bought a new iMac 21.5 inch, 2017. It was doing well on Catalina. Then upgraded to BigSur and it is the worst experience I ever had in more than 30 years using Mac. Slow as hell.

And nobody from Apple has wrote a solution to this issue???

kimeebear OP

Jun ’21

The only solution that worked for me was to uninstall Big Sur and run my macOS on Catalina. I have a 2018 Macbook Pro. Never any issues prior to installation of the new OS. I installed Big Sur as soon as it came out. Does anyone have an update?

juragermanyuk OP

Jul ’21

Damn, guys, can you please fix THAT SH*******!!!!!! I have to work with this FA******* MAC!!!!!!!!!

brerlappin OP

Jul ’21

Someone on Reddit claims the 11.5 beta is faster with fusion drives. Fingers crossed it really is.