I have screwed up my vintage 2012 Mac Pro I won’t tell you how I got here because I hardly remember myself. Something about reassigning the start up disk (I have two 2T discs).
When I turn on the Mac it sounds like a vacuum cleaner. Then a light gray screen followed by the message “Your computer restarted because of a problem…”
Then the Apple logo and the beginning of a progress rule.
Then is a lot of code, beginning with “panic (CPU…”
I have no advice, but I wanted to say that since a rather horrible experience the last time I upgraded the OS, I’ve taken to backing my computer up on a removable 1 TB hard drive every few weeks or so.
Hold down the option key as you boot and see if it lets you pick a different partition to boot from. “But I don’t have a different partition to boot from!”, you may be thinking. But I bet you do. MacOS from approximately 10.7 onwards automatically creates a hidden partition and installs a copy of the base OS along with Disk Tools onto it.
Doesn’t that kind of, like, nuke your files and your settings and your installed 3rd party apps and essentially erase everything you’ve ever done on your computer?
ETA: I’ve never done that. Worst I’ve ever had to do was scavenge a hard disk to salvage my files and then reinstall the OS after reformatting the partition. And that was once in 32 years of using Macs.
Telephone AppleCare. Even if your AppleCare has expired on your Mac, Apple will still help you and walk you through what to do. Also, you can bring it to an Apple Store. Your system isn’t that old.
I’ve been using the Macintosh for decades and they have never failed me. I can’t say the same for Windows computers and stopped using them many years ago.
Do you have a Mac OS disc you can boot from? Insert the disc and hold down the C key to boot from it.
If not, do you have an 8G or larger USB key and another mac you can use to download and create a USB startup disk?
If your problem is that your mac is confused about where to start from, then starting from an OS install disk should work. If those don’t work, then the issue is probably something else. Could be some kind of hardware failure.
The “vacuum cleaner” sound is the fans spinning up to full when starting, which might just be a normal self-test when things didn’t shut down properly (which they haven’t because it’s not booting correctly). The Mac is like: “huh, something didn’t work last time. Let’s make sure I can crank the fans all the way up in case I failed due to overheating last time.”
If you get the message about the Mac not shutting down properly it is usually because it detects that the files systems don’t have the clean flag set on them. It will then perform a full file system check. This will take ages. Normally the file system will survive a bad shut down (any modern journalled file system should usually) but sometimes it can’t guarantee things.
However what you have sounds a lot like a fault deeper. It may be that the boot block is bad on one disk. It is always important to read the error messages, but most importantly the first message.
The default action most computers take with controlled fans is that in the absence of information to the contrary they run the fans flat out, waiting for the temperature sensors to be configured and deliver sensible readings.
Not seeing the option key is really odd. That is very deep in the system.
Could the not recognizing the option key be due to using a wireless keyboard? I know I’ve had to dig up the wired keyboard from my closet in years past when it wasn’t responding to wireless keyboard commands upon booting.