Given I do not have the Thumb Drive or spare bootable drive (without erasing one of my backup drives for the 27”), wouldn’t my original installation disks fully erase the drive before installing? If so, what’s next?
Not unless you ran Disk Utility from the original install disk before installing, otherwise they simply overwrite what is there and given the history of your Mac that could result in software compatibility issues.
Available tools are: Original installation disks, original Snow Leopard disk.
A
16GB thumb drive costs less than $9 USD with overnight or even same day delivery.
On the first go round, the original install disks then had two consecutive on-line updates. I now wonder if they are suspect. i.e. if Apple doesn’t keep some major upgrades, why would they keep old updates?
You are very unlikely to find them if they exist at all.
How big a jump can I actually make from the original install disks? Although the advice is that the size of the jump shouldn’t matter, every upgrade has minimum system requirements.
Any limits are hardware based and the system requirements are:
El Capitan: iMac (Mid 2007 or newer), or MacBook (Late 2008 Aluminum, or Early 2009 or newer), or MacBook Pro (Mid/Late 2007 or newer), or Xserve (Early 2009), or MacBook Air (Late 2008 or newer), or Mac mini (Early 2009 or newer), or Mac Pro (Early 2008 or newer), 2 GB of memory, 8.8 GB of available disk space, and OS X v10.6.8 or later
Sierra: Mac (Late 2009 or newer), or MacBook (Late 2009 or newer), or MacBook Pro (Mid 2010 or newer), or MacBook Air (Late 2010 or newer), or Mac mini (Mid 2010 or newer), or Mac Pro (Mid 2010 or newer), 2 GB of memory, 8.8 GB of available disk space, and OS X v10.7.5 or later