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To give some background, the reason I want to know this information is because, I recently bought a brand new SSD to place into a 2009 Mac mini, where I want to install Kubuntu. I know that PCs store their BIOS in the motherboard ROM, but not entirely sure for Macs.

The problem I have is that if I swap the internal HDD (without copying data to the new SSD) in the Mac, will it mean I can't boot from USB when I have swapped out the hard drive, as the USB boot menu will be wiped, or is this menu stored somewhere else, meaning that I can still access it without copying my hard drive data to the new SSD?

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There really isn’t any difference between where the EFI holds the boot info from pre 2009 and post 2009 Macs

Basically, the boot manager resides in the EFI which of similar to the BIOS in a PC. It’s just the bootable part that loads the kernel is located on the drive itself. So, you can put a blank SSD into a Mac and the boot loader will work, it just won’t find anything to load.

Now the difference in pre and post 2011 Macs (generally speaking) is if the Mac supported Internet Recovery or not. If it did, you could load an operating system (Recovery) off the Internet even with a blank SSD. If you can’t use Internet Recovery, you’ll need bootable media like a DVD or USB stick to install the OS. Once the OS is installed, you’ll her a boot partition and a Recovery partition that you’ll be able to see and select with the boot manager (by holding Option when booting).

So bottom line, even if you have a blank SSD in your Mac, if you have a bootable volume attached (like to USB) the boot manager will find it and boot from it or display it as an option (holding Option when booting )

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  • Many of the 2010 models could also use Internet Recovery after a firmware update. The models are listed at the Apple website Computers that can be upgraded to use OS X Internet Recovery. The Mac Startup Manager (or boot manager as you refer) will find most OS X, macOS and Windows operating systems, but can miss other operating systems that the firmware boot loader is capable of starting. – David Anderson Jun 17 '20 at 10:57
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Yes, if you put a blank SSD inside, you will still be able to boot to an external USB.

Any Recovery Partition would be on the old disk; but the bit you need just to boot up a volume is elsewhere on the board.

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