Startup disk selection issue

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Level 1

6 points

Startup disk selection issue

I have a 21.5-inch, Late 2013, 2.7 GHz Intel Core i5 iMac

On the built-in SATA Hard-drive I have High Sierra OSX installed - I retain it because I have several applications which don't run on anything more recent.

I have an external SSD with Catalina OSX attached via USB which is my boot drive for everyday purposes. (also this SSD is divided and has Mojave as well)

Everything was running fine until recently - I could reboot, hold down the OPTION key and select which disk to boot up in.

But now when I restart (from the Apple menu) and hold down the OPTION key it only shows the internal HDD - no SSD nor Time Machine Drives (SATA connected via USB). I have to press the Power button and physically restart, and then hold down the OPTION key - only then does it gives me the full range of bootable drives.

Selecting which startup disk in the system panel isnt the issue. It seems to be something to do with it not recognising external drives (even time machine ones) from the Menu Restart.

I've tried resetting PRAM, also left it unplugged for a time. No joy.

My only other piece of info is that this seemed to start when I was updating Catalina - always a bit of a pain when located on an external disk. I wonder if there is something left unfinished - but that might be a red herring.

Any ideas?

Posted on Jan 13, 2021 7:18 AM

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Answer 1

Top-ranking reply

rkaufmann87

Level 10

143,784 points

Jan 13, 2021 8:59 AM in response to revjmark

The first thing I would do is do is 3-4 SMC resets back to back and please do them with all wired external peripherals (external HD, printers, scanners etc) disconnected and also reset the NVRAM again with the wired external peripherals disconnected. Then connect the external SSD you want to use and re-test.

SMC Reset & NVRAM Reset

If those do not work, then I suspect you may have some adware installed on the computer. To check for that and to get rid of it, please download malwarebytes (free version) from their website and run it. Then retest again.

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Answer 2

rkaufmann87

Level 10

143,784 points

Jan 13, 2021 8:36 AM in response to revjmark

You can save both you and us a lot of time and effort if you do the following:

Please navigate to the Mac App Store or navigate to www.Etrecheck.com and download the free version of EtreCheck. Once you have you downloaded the app and installed it, please run the report and save it. This report will help us get a good idea what has been installed on your system and help us be able to diagnose what may be wrong.

When you have your report, you can attach it when you reply to this message and we can then review it and help you determine what is needed

to get your system running well again.

For instructions on how to download your EtreCheck report and attach it to your reply to this message please click https://discussions.apple.com/docs/DOC-250000211

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Answer 3

revjmark Author

Level 1

6 points

Jan 13, 2021 10:15 AM in response to rkaufmann87

Thanks again for your time. Much appreciated. This has helped me narrow down the problem. As I plugged my drives/peripherals back in one at a time - it seems that one of the external drives is causing the problem. It has no OSX on it, but it seems to prevent the SSD from being recognised without going into a power off/on restart.

I'm not sure what I do to solve this! Any suggestions gratefully received.

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