Refurbished iMac Retina 4K, 21.5-inch

The reason your iMac is slow is due to the 5400-rpm hard drive. While this hard drive found in your Mac is perfectly suited to light tasks, such as email, web browsing, etc., for more advanced tasks, and for users who want the maximum performance from their Mac, this hard drive does have its limitations. Luckily, you can use an external SSD as your startup disk to run macOS and all your data from that. It will make your Mac 10 to 30 times faster for storage, and in turn, make your entire Mac system much faster. For more info, instructions, and what external SSD to buy, please see: How to Setup and Use an External SSD as your Startup Disk on a Desktop Mac - Apple Community.

Another option is to replace this Mac with a new Apple Silicon Mac: Mac - Apple. If you go this route, it is generally recommended that you purchase 16GB of Memory with the largest SSD that you can afford. You can also use Apple Trade-In to get credit towards a new Mac: Apple Trade In - Apple.

Jack

I don't see any of the usual suspects. The report is rather clean.

The report does note "Poor performance - EtreCheck report shows poor performance. This is unusual". The only thing that's obvious for the poor performance is what was pointed out earlier: the 5400 rpm boot drive.

If you were to get and external SSD you could improve the read and write

Write speed: 81 MB/s

Read speed: 73 MB/s

capability by approximately approximatly 6x or more. I have several external SSDs and their read/write speeds are in the neighborhood of:

Write speed: 486 MB/s

Read speed: 500 MB/s

This would increase your boot speed, app opening and closing speed, file opening and saving speed and anything associated with reading or writing from the disk.

I have a couple of external SSDs with other systems on them and boot time on them is about 40 seconds.

Additional RAM allows you to have more files or windows opening without having to cache them to disk which is a slow one. Since it's not practical to increase the RAM in your model your best solution is an external SSD and clone your boot drive to it with Carbon Copy Cloner and run from it.

Your problem is you bought a base model iMac, the machines were never intended to do anything more the basic e-mail and light web surfing and you are. using professional grade apps on it. In short you bought the wrong machine for the workflow you have. By the way, using Chrome is a problem, Chrome is a HUGE RAM hog and should be avoided if possible.

The bottleneck is the 5400 RPM HD and there is NOTHING you can do to speed these up. The only thing you can do to improve performance is to buy a Thunderbolt 3 external SSD and clone the internal HD to the SSD and then mark the SSD your startup drive. Then the machine will be quick! The SSD I'd recommend is the OWC Envoy Pro EX Thunderbolt 3, however if budget is a problem then a USB 3 external SSD will be a solution. In that case the following is fine, OWC On the Pro Go Power Adapter & the OWC On the Pro Go Power Adapter.

If the computer is less than 14 days old, then I'd replace it and buy any Mac with at least 16GB of RAM and the highest capacity SSD you can afford. Moving forward, please do not buy on price, estimate your work flow and ensure the computer you are considering is up to the task before pulling the trigger.

Jopibo wrote:

Just checked: Apple would give me 360$ for it.

I purchased it last year and it cost me 1,500$!!!

You don't necessarily need to trade it in. Simply use an external SSD (How to Setup and Use an External SSD as your Startup Disk on a Desktop Mac - Apple Community.)

I bought this same type entry level: 2015 21.5" iMac Retina bought new; 1TB 5400 RPM HDD and all.

Performance never got any better than what you're experiencing until I started booting from an external SSD. At the time (2020), $100US made for a 5x improvement in disk read speed: 93MBps vs 460MBps. The difference marked an enormous performance increase. The external drive was a Samsung T7 500GB; very small and light and thermal tape stuck it security to the back of the case.

You may feel like you're "fixing" something that shouldn't be "broken", but this is the only practical fix for a slow internal HDD.

In order to learn more about your setup and hardware please download and run Etrecheck.  Copy and paste the results into your reply. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the first window that comes up so that it can get additional information from the Console and log files for the report:

Also click the About… vurron and read the info to further permit full disk access.

Copy the report

and use the Additional Text button to include the report in your reply.

Then we can evaluate the report and see if we can determine if there's any software issue that's contributing to the performance problem other than the hardware. It also will give us a better understanding of exactly what hardware you have, i.e. RAM, drive type and rotational speed and real world performance indicators.

The computer has been in service for over a year so you cannot return it. The reason you would want a SSD is that they are dramatically quicker than a traditional HD. The bottle neck in computers the past 15 + years has not been the CPU or RAM it has been the use of mechanical HD's which date back to the 1950s! Another advantage is SSD should be more reliable than a traditional HD as there are no moving parts to wear out.

You can post an EtreCheck report and we can look for anything else that could slowing down the computer such as having a third party antivirus, cleaning app or any other types of third party "maintenance" apps installed. I would recommend posting an EtreCheck report as then we can look for any issues that may be causing the problem. Nothing to worry about though EtreCheck is 100% safe and does not post any type of personal information. Please read Old Toad's instructions, they are simple to follow and thorough.

Your Mac appears to have the same super slow 5400 rpm hard drive; it is as slow as molasses. There is nothing you can do to speed it up; the only thing would be an external hard drive which you would use as a startup disk and forget about the internal drive. Running Cocktail is a waste of time; those utilities were ok with earlier OS versions, but not with the latest ones.

By the way: It is best to start your own thread; tagging onto an old one usually is not all that helpful especially if it has been marked as solved.

Hi, Jopibo, i can try to help you, a bit… the RAM is upgradeable, if you take it to an Apple Authorized Service Provider. If you suspect you have malware , which you might have ( probably not though) then Malware Bytes will help you out with that. As rkaufmann87 mentioned, you do have a conventional hard drive ( fusion drive? ) … replacement of that with an SSD would be helpful. However, both the ram upgrade + replacement of the hard drive with an SSD cost money ( plus you have to factor in labour, etc) , and you do have up to 14 days from when you bought it to replace it.. however, upping the ram to 16 gigs + and swapping out your conventional hard drive for an SSD or getting an external one would be helpful… but i’d get an estimate from an AASP , price it out before deciding to do anything

john b

What does it mean that the telephone support is over? I have had the same slow problem to solve on an 2015 iMac 16,1 and they have been there for me on multiple calls for the same case.

As it goes, I had to erase the HDD but 1st use Boot Camp to remove the partition Windows was on. Simply erasing the HDD would not fix the lagging like removing the partition did this week!

See if there is a partition on yours. By now you have learned the start with Cmnd R to run disk util?

I am scheduled to get the HDD replaced in this 16,1 iMac with a 250GB SSD

But what I don't get is how come the HDD makes so much noise like it's scrambled and needs to move the read head all over the platter? While computer seems to be lagging is when you can hear that HDD chattering if you put ear on screen. And that can take 2 minutes. I wonder how much noise Jopibo computer's HDD makes?

I'll add my 2 cents -

the bottleneck is the 5400 rpm drive; it is slower than molasses. I know because - before I got smart - I had a Mini with a 5400 rpm drive. It was absolutely worthless; you could have dinner and a movie while waiting for simple things. Upgrading to the latest OS will not help.

a Genius once told me years back to run Cocktail

what about that? You buy it once and it allows updates as the OS is updated.

it seems to allow to clean up and tweak things over my head, that being said it has an auto mode too

I too am looking for a refurbished one. I plan to take into store so the genius can run their hardware diagnostic stuff. Have you tried? They will if you schedule an appointment.