3 GHz 6-Core Intel Core i5 Mac running slow, particularly on start up

Hi everyone


Struggling with my Mac at the moment in that it's running slow. I've run a report on EtreCheck which can be seen below - it would be great if I could have some guidance as to what I do next please!


Thank you in advance



Posted on Oct 5, 2025 2:31 PM

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Question marked as Top-ranking reply

Posted on Oct 5, 2025 2:52 PM

All Intel product marketing aside, the performance of a computer is based on the slowest component, and not based on the fastest. Best performance (and price) comes from a balance of components, where one fast component can be stalled waiting for slower components to catch up.


The 8 GB and the hard disk drive (Fusion, here) are hindering your performance here.


The limit here is likely the lack of memory.


Here is why:


Why is my hard disk drive iMac so slow? - Apple Community


The least expensive option for improving performance — short of replacement — is usually an external SSD. And it probably won’t help all that much, given this looks like insufficient memory. Though maybe the Fusion is failing?


Use an external SSD as your startup disk … - Apple Community


Upgrading the internals of an iMac 21.5” iMac is an expensive and somewhat risky slog.


This thing is also seriously under-configured — or sometimes called “under-purchased” — for what is running.


It can also be somewhat possible that the hard disk is failing, and you will always want to have current backups anyway, but this looks more like Microsoft Office and Adobe Creative Cloud — neither of these app suites are lightweight — on an under-configured iMac.


To check the storage hardware, run Apple Diagnostics and DriveDx:


2 replies
Question marked as Top-ranking reply

Oct 5, 2025 2:52 PM in response to parky80

All Intel product marketing aside, the performance of a computer is based on the slowest component, and not based on the fastest. Best performance (and price) comes from a balance of components, where one fast component can be stalled waiting for slower components to catch up.


The 8 GB and the hard disk drive (Fusion, here) are hindering your performance here.


The limit here is likely the lack of memory.


Here is why:


Why is my hard disk drive iMac so slow? - Apple Community


The least expensive option for improving performance — short of replacement — is usually an external SSD. And it probably won’t help all that much, given this looks like insufficient memory. Though maybe the Fusion is failing?


Use an external SSD as your startup disk … - Apple Community


Upgrading the internals of an iMac 21.5” iMac is an expensive and somewhat risky slog.


This thing is also seriously under-configured — or sometimes called “under-purchased” — for what is running.


It can also be somewhat possible that the hard disk is failing, and you will always want to have current backups anyway, but this looks more like Microsoft Office and Adobe Creative Cloud — neither of these app suites are lightweight — on an under-configured iMac.


To check the storage hardware, run Apple Diagnostics and DriveDx:


Oct 7, 2025 5:51 PM in response to parky80

This section, which usually throws out the Big Red Flag with slow iMacs, does not look too bad:


Performance:

System Load: 1.80 (1 min ago) 1.52 (5 min ago) 1.04 (15 min ago)

Nominal I/O usage: 3.35 MB/s

File system: 21.71 seconds

Write speed: 534 MB/s

Read speed: 1062 MB/s


Poor drive access speeds are the usually cause of "slow" reports with 21.5-inch iMacs models between 2012 and 2019. Yours speeds are a bit under expected for that model but not by much. I would not suspect that as the main issue in your slowness. I have an older Mac laptop with an old-school aftermarket SSD and it does 500MB/sec either way and does not feel slow.


Expected speeds for Fusion in your iMac model are Writes 500-900 MB/sec, and Reads around 1200-1300 MB/sec. An external SATA 6 SSD will for about 500MB/sec both ways and would make this worse. You can used a ThunderBlot 4/5 external drive and see speeds up to 2700MB/sec both ways.


The "File system" time is a check of relative drive health. Yours shows good (anything under 30 seconds).


OneDrive could be an issue if you have a slow internet connection. The quickest way to check internet speeds without being smacked with ads is to use Netflix's fast.com site. Works even with very old browsers.

3 GHz 6-Core Intel Core i5 Mac running slow, particularly on start up

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