[Solved] Can't boot from external drive (clone of internal)

[Pyx69]

Hello,

I hope you can help with the following boot issue:

- I cloned my El Capitan internal HD to a new SSD , then swapped disks and all works perfectly.

- Now I want to test upgrade to High Sierra on the old HD connected to external usb3/sata.

At boot from bios I select the Efi partition on external HD, it boots, but then the boots continues from SSD , I can see it from blinking lights and speed.

What I have to do to boot from external and leave SSD untouched?

I'd like to avoid swapping disks again...

Thank you!
P.

 

[Bob_the_Tomato]

I would check the hardware that you are using to attach the internal HDD to the USB port.
Does that how allow booting from external drives?

 

[Pyx69]

I would check the hardware that you are using to attach the internal HDD to the USB port.
Does that how allow booting from external drives?

Thank you for your suggestion.

The cable is this: https://www.amazon.es/dp/B073QG493V/?tag=tonymacx86c03-21

I can't find documentation about boot features.

 

[Bob_the_Tomato]

Look carefully at the pictures in Amazon. That adapter does not provide power to the HDD only to SSD's since they can draw enough power from the USB 3 port. And HDD cannot.

 

[Pyx69]

Ouch ! You're right.

I will buy an enclosure.

Thank you very much!