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Aboo

macrumors 65816
Original poster
Jul 7, 2008
1,017
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Hi,

Trying to do a complete clean install of my 7,1 Mac Pro with a fresh copy of catalina. I followed the instructions to download the installer file and create a bootable USB drive for installation. I enabled boot from external devices in the boot security utility. Everytime it boots from the USB drive however, the setup reboots and either goes into the already installed Mac OS or into the recovery partition.

I thought my install drive could be faulty so I re-created one, but still experiencing the same issue. I recall this process being much easier on earlier Macs but haven't quite figured out the easiest way to do it with Catalina. Are there any trusted forum step-by-step instructions for making a boot disk, that may perhaps be useful, or am I overlooking something minor that would help solve this?

Thanks!
 
Once you boot off of the USB installer go to "Startup Disk". If the USB installer is OK then your Catalina USB drive should appear in the box. Select the drive and it will reboot into Catalina. And yes things have been changed and I believe it has something to do with the new BootRom updates.
 
Hi- I'm not sure what a 7,1 Mac Pro is exactly.

There is a known issue with newer T2 hardware security-based Mac's running Catalina refusing to boot from some external drives. Mike Bombich's site has an excellent summary and list of drives toward the bottom of the web page.

In my case I could not boot from the newest version of a WD My Passport Ultra for Mac. I have an older version of the same drive that boots externally no problem.
 
Hi- I'm not sure what a 7,1 Mac Pro is exactly.

There is a known issue with newer T2 hardware security-based Mac's running Catalina refusing to boot from some external drives. Mike Bombich's site has an excellent summary and list of drives toward the bottom of the web page.

In my case I could not boot from the newest version of a WD My Passport Ultra for Mac. I have an older version of the same drive that boots externally no problem.

The 7,1 Mac Pro is the late 2019 Mac Pro. I will look at that article too, thank you!
 
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