Sorry for weird headline. What I mean is this:
When starting a Mac and before the OS on a disk kicks in, some "memory" inside The Mac's dungeons knows e.g. which disk is supposed to be used. If I press alt/option button at startup, this "memory" opens a selection of available disks. And so on.
What is this unit/gadget called? Can it be replaced, updated or repaired?
If I press alt/option button at startup...
That startup combo opens the startup manager:
Change your Mac startup disk - Apple Support
If you are having issues, please elaborate and we may be better able to assist. Please include which Mac is involved and its current macOS version.
NVRAM cannot be replaced but can be reset. HOWEVER, please do not go there until you share the issues, if any, that caused you to ask. A reset may not be the appropriate action.
It's the NVRAM, or on earlier Mac models, the PRAM, and isn't upgradable or replacable by customers.
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A slow and sluggish computer will usually be due to one of two things. A worn out or failing hard drive, or a software issue. You can check the health of the hard drive(s) by running DriveDx and posting the complete text report here using the "Additional Text" icon which looks like a piece of paper. If you are using hard drive (as opposed to SSDs), then any "Warning" or "Failing" notices indicates a worn out or bad hard drive respectively.....and the hard drive needs to be replaced. Assessing the health of an SSD is not as easy and requires a manual examination of the SSD's health information.
An issue with the file system could also cause performance issues, so you may want to run Disk Utility First Aid on drive. Even if First Aid says everything is "Ok", click "Show Details" and scroll back through the report to see if any unfixed errors exist.
Normally we would suggest running the third party app EtreCheck so we can examine its report for clues, but EtreCheck now requires macOS 10.13+ IIRC. You can try booting into Safe Mode to see if performance improves.
You can also try running the Apple Diagnostics to see if any hardware issues are detected. The diagnostics may report issues if any third party devices have replaced Apple OEM components.
Edit: Forgot to provide the link for DriveDx:
Thank you. You provided a clue:
Finder and apps frequently hangs.
Does that cause kernel panics (KP), showing a screen something like this:
KPs can be due to many things. but the most common is incompatible RAM.
Have you added RAM to the computer above the RAM with which it shipped? Not all RAM is Mac-friendly, even when advertised as such. Most senior contributors here recommend only Crucial of OWC RAM for Macs. Corsair, Kingston, and PNY RAM have all been part of trouble reports here.
Troubleshoot by removing any non-Apple RAM modules and report on what you found.
First: Thanks a bunch for replies.
No, no Kernel Panics. Have 64Gb Ram which has been there since eternity and years before this problem turned up.
Something in the logic board, VRAM or PRAM has obviously resigned. But I knew this was coming. Just glad it did its job this far. It's on its way to the scrap yard.
Again, thanks for all advice.
Ah, thanks.
It's MacPro 5.1 late 2010. Past month been sluggish. Finder and apps frequently hangs. No keyboard shortcuts on startup works, not safe mode, recovery mode, verbose or any other. Have tried using the terminal instead, but no go with that. Maybe I use wrong codes?
Anyway, it seems as if the machine has given up. But I thought I'd give it a final try before it goes into the trash. So any suggestions are welcome.
What is the "first memory" in a Mac called
