OS rewind!……..A little help needed

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I have a late 2015 iMac. It has run slow for a number of years, even with the OS on an attached SSD drive. I decided to restore the iMac to its original OS, but this has caused some issues.

I had to do the shift-cmd-option-R to get the OS to restore, but now I cannot move the OS further than the original which was El Capitan. I have tried to do a software update (of which it says that there are none available) and also visited the Apple download centre to try and manually download the next OS (Sierrra) but it is not available from the site. Any help with this would be much appreciated.

Thanks
 

Raz0rEdge

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That vintage of iMac is able to run macOS Monterrey as the latest version. So if you hav El Cap already installed on the machine, boot into it and visit this link to get the option to download Monterrey from the App Store.


Then create a USB installer with the Monterrey installer using DiskMakerX.


Now boot from the USB drive, erase the contents of the HD ad do a fresh install of Monterrey.
 
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I have a late 2015 iMac. It has run slow for a number of years, even with the OS on an attached SSD drive. I decided to restore the iMac to its original OS, but this has caused some issues.

I had to do the shift-cmd-option-R to get the OS to restore, but now I cannot move the OS further than the original which was El Capitan. I have tried to do a software update (of which it says that there are none available) and also visited the Apple download centre to try and manually download the next OS (Sierrra) but it is not available from the site. Any help with this would be much appreciated.

This is... extremely odd. Are you SURE you are on El Capitan? What does About This Mac say you are running?
 
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Darker Times
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That vintage of iMac is able to run macOS Monterrey as the latest version. So if you hav El Cap already installed on the machine, boot into it and visit this link to get the option to download Monterrey from the App Store.


Then create a USB installer with the Monterrey installer using DiskMakerX.


Now boot from the USB drive, erase the contents of the HD ad do a fresh install of Monterrey.
Thank you.
 
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That vintage of iMac is able to run macOS Monterrey as the latest version. So if you hav El Cap already installed on the machine, boot into it and visit this link to get the option to download Monterrey from the App Store.


Funny how time flies and things change. I totally forgot that we used to have to get new versions of the OS from the App Store. So of course it wouldn't have shown up in Software Update with El Capitan.
 

Rod


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I am a little curious, why did you think your late 2015 iMac would run faster from an external SSD drive?
That device with its 2TB Fusion Drive was supposed to be pretty fast for its time with the 128GB built in SSD running the OS as well as frequently used storage items. I think it's unlikely an external SSD would be faster.
I do know however that some people recently have reported problems with the Fusion drive after the change to the APFS filing system introduced in macOS Catalina.
When did you start having slow down issues?
 
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I am a little curious, why did you think your late 2015 iMac would run faster from an external SSD drive?
The OP has a 21.5" iMac, which isn't as well equipped as the 27" models. It may not have a fusion drive, but an original rotating disk HDD.
 
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I am a little curious, why did you think your late 2015 iMac would run faster from an external SSD drive?
That device with its 2TB Fusion Drive was supposed to be pretty fast for its time with the 128GB built in SSD running the OS as well as frequently used storage items. I think it's unlikely an external SSD would be faster.
I do know however that some people recently have reported problems with the Fusion drive after the change to the APFS filing system introduced in macOS Catalina.
When did you start having slow down issues?
The iMac I have does not have a Fusion Drive, just a regular HDD. I was advised (on some Mac forum or other) that running the operating system from an SSD would improve performance, which was, at best, lacklustre.
 
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If the fusion disk was still intact, it would be more than 1TB. I believe you are only using the HDD portion of the fusion drive. What does Disk Utility (DU) show? In DU, go to the View menu and make sure Show All Devices is selected.
 

Rod


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Sorry but hasn't Darker Times confirmed that this is not a fusion drive? What concerns me is that the 1TB internal drive is Untitled and has virtually no data on it which suggests everything is on the external SSD.
 
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I'd like to see a screen shot of the All Discs Display in Disk Utility.
I maen if it is a fusion drive that would explain a lot.
Hi
It isn't a fusion drive, it is just a standard HDD. Thanks to everyone for their help and advice, as I have now managed to install Mojave and all is running fairly speedy again. When I tried to install the OS at first, the Mac said that it could not find a hard drive to install to. Turns out that the file system on the Hdd had become corrupt, so a reformat sorted that and I was able to install the OS. All seems to be working great, so thanks again for all the help and links to software.
 

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