iMac Late 2015 macOs Monterey is painfully slow

[JGC1986]

I have an 21.5" iMac Late 2015 macOs Monterey that is painfully slow.

Here is everything I have done to try and fix this:
Reset SMC and PRAM
Ran first aid in Disk Utility - no issues
Uninstalled most apps

I cannot get the iMac to boot to any sort of diagnostic or recovery partition at all.

What I ideally want to do is buy a Solid State hard drive, and try plugging it in with USB and cloning the current drive, then format the internal drive and have the iMac boot with the external SSD...I am scared to open the iMac because the top right screen is damaged.

What should I do? Is there anyway I can check to see if the iMac has hardware issues outside of ASD?

 

[Steve121178]

Does your iMac have a slow spinning mechanical HDD? If so, that's 100% the bottleneck.

Since Catalina optimisation for non-SSD's seemed to go out the window. I suppose understandably so in this day & age.

 

[Fishrrman]

You've got a Mac that is almost ten years old.
That is going to figure with anything you do.

Having said that...

I can fix you up.
Just do what follows.

Get one of these:

https://www.amazon.com/SAMSUNG-Portable-Photographers-MU-PE1T0R-AM/dp/B09VLJB2DC/ref=sr_1_3?keywords=samsung+t7+shield+1tb&qid=1706284299&sr=8-3

(how much space is consumed on your current internal drive?)

Download SuperDuper by clicking this link:

https://shirt-pocket.com/mint/pepper/orderedlist/downloads/download.php?file=https%3A//shirt-pocket.com/downloads/SuperDuper%21.dmg

SuperDuper is backup/cloning software.
It's FREE to use what we're going to use it for.

Connect the SSD, use Disk Utility to erase it to:
APFS, GUID partition format.

Open SuperDuper.
It's incredibly easy to understand and use.

Use SD to "clone" the contents of your internal drive to the SSD.
It will take a while, depending on how much stuff you have.
(again, how much space is used on the internal drive, the total space used must be less than the capacity of the SSD)

When done, open the startup disk settings pane.
Select the external SSD to be the boot drive.

Now, REBOOT.
You should get a boot from the SSD, and it should be faster.
Perhaps a LOT faster.

Follow my instructions above, and I predict that you'll come back and say, "I didn't realize it could run this well"...

 

[sdfox7]

Could be a combo of a dual-core CPU, mechanical hard drive, and lack of RAM (8 GB?)

My 2011 iMac with quad core CPU, SSD and 32GB RAM runs Monterey perfectly (OCLP)

 

[Andrey84]

In addition to moving your OS to an external SSD, don't underestimate the speed increase from a clean Mac OS install. Create a bootable USB under the official guidelines here, it's really easy, and install a clean Monterey on that new external SSD. I don't know why exactly, but Mac OS just becomes slower after 3 years of daily use. Clean install kind of wakes the iMac up.

After you've done that, make sure you've changed these Accessibility>Display and Dock settings as well. "Reduce motion" = Yes, "Reduce Transparency" = Yes, "Minimize windows using" = "Scale effect". Make sure you're using a still image and not a Dynamic wallpaper.

 

[rin67630]

Now, REBOOT.
You should get a boot from the SSD, and it should be faster.
Perhaps a LOT faster.

Follow my instructions above, and I predict that you'll come back and say, "I didn't realize it could run this well"...

Now, Reboot and hold down the "alt" key, choose your external drive...
Just to mention for some being unaware of the boot option.
After that go to system preferences and chose the external SSD as the regular startup disk.

 

[rin67630]

I don't know why exactly, but Mac OS just becomes slower after 3 years of daily use

APFS is a HDD killer. It fragments the HDD to death.
Never use APFS on a spinner drive !

 

[exoceano]

APFS is a HDD killer. It fragments the HDD to death.
Never use APFS on a spinner drive !

I have similar issues on a 2019 with HDD - can I make a partition with HFS for the System and boot up files ?

 

[Woodstockie]

Most likely your HD is the problem there. I have the bigger brother of yours and even though I have the 128GB SSD for startup, the 2TB HD made it so slow to work with. I run the iMac now from a Firewire 800 external disk with a SSD in there. Running OCLP with Sonoma, it boots and runs much faster.

 

[rin67630]

Most likely your HD is the problem there. I have the bigger brother of yours and even though I have the 128GB SSD for startup, the 2TB HD made it so slow to work with. I run the iMac now from a Firewire 800 external disk with a SSD in there. Running OCLP with Sonoma, it boots and runs much faster.

Firewire... Sounds like a very old system. Exoceano has a 2019 iMac.

 

[rin67630]

I have similar issues on a 2019 with HDD - can I make a partition with HFS for the System and boot up files ?

A 2019 iMac should have a Fusion drive with a 128GB NVMe blade isn't it?
If yes you can get it flying with current macOS versions. You will not even have to open the iMac...
Can you confirm my assumption?

 

[DeltaMac]

The base (cheapest) 2019 21.5-inch iMac came with an HDD - a 1TB with 5400-rpm spinning rust.

 

[rin67630]

The base (cheapest) 2019 21.5-inch iMac came with an HDD - a 1TB with 5400-rpm spinning rust.

What a holy peace of cr*p ! How could Apple sell in 2019 a computer with only a spinning drive as storage?

For that one a good solution is to use an external USB3 SSD.

Better a real Thunderbolt 3 SSD case with an NVMe blade (not that easy to find, but really worth the additional price).
That is a better solution than opening the iMac to replace the HDD with an SSD (which will be SATA, slower than NVMe over Thunderbolt3)
The small external drives can be glued behind the stand, barely visible and not dangling on the desktop.
The internal HDD can be used as a time machine storage.

 

[bousozoku]

In addition to moving your OS to an external SSD, don't underestimate the speed increase from a clean Mac OS install. Create a bootable USB under the official guidelines here, it's really easy, and install a clean Monterey on that new external SSD. I don't know why exactly, but Mac OS just becomes slower after 3 years of daily use. Clean install kind of wakes the iMac up.

After you've done that, make sure you've changed these Accessibility>Display and Dock settings as well. "Reduce motion" = Yes, "Reduce Transparency" = Yes, "Minimize windows using" = "Scale effect". Make sure you're using a still image and not a Dynamic wallpaper.

Using OnyX would probably allow you to do some maintenance to clear out the cobwebs.

 

[rin67630]

I have similar issues on a 2019 with HDD - can I make a partition with HFS for the System and boot up files ?

Forget the HDD for anything other than TM or data storage.
Use an external Thunderbolt3 SSD, your iMac is worth more than spinning...
Look at post #13

 

[exoceano]

What a holy peace of cr*p ! How could Apple sell in 2019 a computer with only a spinning drive as storage?

For that one a good solution is to use an external USB3 SSD.

Better a real Thunderbolt 3 SSD case with an NVMe blade (not that easy to find, but really worth the additional price).
That is a better solution than opening the iMac to replace the HDD with an SSD (which will be SATA, slower than NVMe over Thunderbolt3)
The small external drives can be glued behind the stand, barely visible and not dangling on the desktop.
The internal HDD can be used as a time machine storage.

Thanks - yes it has a HDD as DeltaMac describes - Thanks all for the guidance - I will look for an NVMe lade and move to the SSD solution - Securing it to the back of the stand is a nice fix too - Thanks much - good to have this community to lean on - Been a Mac user since '86 - I guess I should be smarter !

 

[DeltaMac]

I suggest replacing the blade SSD internally, but then I have done that upgrade several times in the past, and it's just a matter of following a few steps, and gives a better response from software- but experience helps with that job, too.

 

[rin67630]

I suggest replacing the blade SSD internally, but then I have done that upgrade several times in the past, and it's just a matter of following a few steps, and gives a better response from software- but experience helps with that job, too.

Are you sure there is a blade connector inside?
On previous models, the base iMac sold with only a HDD did not have that connector.

 

[exoceano]

I don't think I can manage an open and install - I think a case and an external SSD solution is more in my skill set - I have done memory installs before but nothing where I needed to remove the display

 

[rin67630]

I don't think I can manage an open and install - I think a case and an external SSD solution is more in my skill set - I have done memory installs before but nothing where I needed to remove the display

it's also the easiest and safest way to get your iMac to fly again.
Dismanteling the iMac up to the accessing the blade connector under the logic board is painful and risky.

 

[DeltaMac]

Are you sure there is a blade connector inside?
On previous models, the base iMac sold with only a HDD did not have that connector.

There still might be a blade connector, but, if it did not come with a blade drive, the only way to find out for sure, is to open it up, and take a look. I have added a blade NVME drive to 2 different 21.5-inch iMacs, one 2013, and a 2017. Both had open blade connectors, and I was upgrading from a single SATA HDD on both. But, I have also opened up a 2014 that did NOT have a blade connector. THAT's a lot of time, just to look on the back of the logic board. However, I could also upgrade the RAM (while I was that deep), so -- even without an NVME upgrade, there was some value to removing the logic board. It's the only way to upgrade RAM on a 21.5-inch iMac.
The only iMac that I studied some more was the 2013. It appears that later in the manufacturing period for those, they began producing only two slot (SATA + blade) logic boards, so at some point, it did not matter if you bought the standard HDD, there was still an empty, unused slot. I would consider that a bonus. But, again, Apple doesn't tell you which ones, and there's no way to find out unless you open 'er up, and look for yourself. There's probably a model number somewhere on the logic board, from the original build, but I never looked for that,

 

[DeltaMac]

I don't think I can manage an open and install - I think a case and an external SSD solution is more in my skill set - I have done memory installs before but nothing where I needed to remove the display

OP has a 21.5-inch iMac. If you want to upgrade the RAM - you have to remove the logic board. There is no handy door on the back, and the RAM slots are on the back of the logic board.

 

[DeltaMac]

it's also the easiest and safest way to get your iMac to fly again.
Dismantling the iMac up to the accessing the blade connector under the logic board is painful and risky.

I agree to some extent. But, with some patience, careful work, with good steps to follow (iFixit.com is usually pretty good with that), without hurrying, you can do that kind of upgrade successfully!
Again, the OP has a 21.5-inch iMac, and you should always consider RAM upgrades, beyond the SSD install. Either will need the logic board pulled. Order your replacement tape strips before you start

 

[Fishrrman]

OP seems to have disappeared...

 

[rin67630]

I agree to some extent. But, with some patience, careful work, with good steps to follow (iFixit.com is usually pretty good with that), without hurrying, you can do that kind of upgrade successfully!
Again, the OP has a 21.5-inch iMac, and you should always consider RAM upgrades, beyond the SSD install. Either will need the logic board pulled. Order your replacement tape strips before you start

I have done it. I had to do it because the SSD blade was defective, causing loooong boot times.
Honestly, if I can avoid it, I would.