IMac 21.5" 2012 - White Screen Boot Struggles

[Gene Jacket]

Hi everyone!

I come cap in hand, hoping for some guidance to keep my old iMac going. I'll try to explain as much as possible, but am happy to provide whatever extra information would help...

History​

• Jan 2013: Bought the 21.5" Late 2012 model, spec: 2.7GHz Quad-Core Intel Core i5, 8GB 1600 MHz DDR3, NVIDIA GeForce GT 6400M 512mb.
• Jun 2018: HDD on the fritz; bought a SSD that's driven it ever since. Internal HDD still there as an empty shell.
• Aug 2019: Power supply blew up. Apple Store replaced it (after telling me it's an obsolete model and I was lucky they had a part for it...)
• Jan 2024: Already restricted to Catalina 10.15.7 for a long time, now most apps I use announce they're going to stop working. So...

Decision Time:

1. Get rid
2. Hack upgrade to a newer MacOS (via OLCP?)
3. Install Linux

I've been trying for Linux because I like it, and as far as I'm aware it's compatible. But I've really never got to try installing it due to boot issues. The Mac did somewhat recently get stuck in a boot cycle (try a bit, restart itself etc), but after some resting it somehow eventually loaded up properly.

Current Issues​

So with a live USB ready to go I restarted it and tried for the boot menu. But it wouldn't give me the boot menu. It also wouldn't load recovery mode. It would get stuck at the loading screen. Eventually, somehow (via a bunch of restarts), it loaded up normally. In the terminal I edited the nvram (as per this guide) to force the boot menu so I wouldn't need to try to Alt/Option method on startup. Did that, forced a restart, and since then I've been unable load it back up properly.

Mostly I get the white screen and nothing else. No Apple logo, no loading bar. None of the startup shortcuts keys work, EXCEPT for resetting nvram (alt/option+command+r+p) which works every time. So keyboard input surely isn't an issue. Sometimes I reset the nvram once, sometimes I do it like 3-5 times in a row which I've seen people say helps to do a *proper* reset.

For a while, somehow, some things started working. Single-user mode brought some code up (then seemed to stick; never saw a terminal), so I tried verbose mode which started working too. Sometimes it'd get stuck so I'd try again from scratch, and eventually it'd fly through a bunch of code before leading me onto an Apple logo and loading bar. Sometimes it'd stick, other times it'd end up looking quite promising with a grey screen and some "please connect mouse/trackpad" type prompts. This proved a dead end, sadly. My USB mouse didn't register, nor did the bluetooth mouse. *shrug*

One time after restarting from this mouse/trackpad screen, pressing alt/option did bring the boot menu up. I choose EFI (live USB inserted already), and it looked briefly like it was working with terminal output zipping away, but then it got stuck and stopped. Around this time safe-mode did actually present a circle error message instead of doing nothing.

For quite a while I jumped between all these things trying to get somewhere, but eventually everything stopped working again. Back to white screen only, nvram reset being the only key combo to do anything. I long for verbose mode to bring me a bit of hope again!

Throughout this I've tried the SMC reset, all combos of key shortcuts I can think of, a series of live USBs stuck into various USB ports (with and without the original SSD); peripherals all in and out. I feel like I've exhausted the combination of things that could be plugged in or removed (but am happy to try any of them again).

This morning I tried a live USB of rEFInd hoping it'd somehow jump in before any other boot process and allow me to see access the Linux USB, which I could then put onto the SSD. No luck. White screen only. Again, combo of drives tried.

What now?​

At this point I'm at a loss and wondering if there's some kind of logic board / hardware issue at play, in which case the thing would need opening up... which might be an expense/effort too far.

If anybody here has any thoughts or advice for things I could do, I'd really appreciate it. I'm keen to try whatever I can before getting rid of what is still a beautiful machine. Before things went haywire it was still running as smooth as butter (once actually booted up...)

Things I have/know that might help:

• Endless external hard drives / a new Sandisk USB 3.0 128gb to flash whatever is needed
• Knowledge that all of these drives (including the SSD), when plugged into the MBA, appear fine (and pass First Aid without issues)
• A Linux ThinkPad ready to do whatever
• A recent Time Machine backup on an external drive
• Access to a MBA.
• A lack of concern for the iMac's personal files (everything I care about is already on multiple other devices)

So that's where I'm at. If there's anything else you'd like to know, please do ask!

Thanks for reading!

 

[Rodananne]

You have plainly invested a lot of time and effort in getting this device up and running again which is the only reason I did not immediately suggest that you scrap it and buy a new device.
I'd suggest that, rather than waste the knowledge you have accumulated you look at getting another "newer" not necessarily new iMac that you can tweak to do what you want. Especially if you are interested in Linux. The only other alternative you have is to pay top dollar for a current model Mac.
I don't think your existing iMac is saveable, it sounds like several things could be wrong with it and at 12 years old, well, that's not surprising.

 

[MacsBug]

One thing that I didn't read that you had tried is to zap the PRAM. To do this you should have a wired Mac keyboard and hold down the Command Option P and R keys as soon as you hit power. Then let the 4 keys go after you hear a 3rd chime. At that point you should be able to hold down the Option key to get to the boot menu.

As far as OCLP goes, you can use it to install a newer OS (Big Sur or Monterey), but I wouldnt go up to anything newer than that on a 2012 Mac. If you do install OCLP, you may want to isntall the drivers on both the inetral and external drive. These get installed by the software on the EFI partition.

You can always try to install Linux on the external drive, but this is not something that I have ever done, I have always installed it on internal drives. I am not sure if anything is needed to boot from linux on an external. This may be dependent on what flavor bistro that you use.

 

[Gene Jacket]

You have plainly invested a lot of time and effort in getting this device up and running again which is the only reason I did not immediately suggest that you scrap it and buy a new device.
I'd suggest that, rather than waste the knowledge you have accumulated you look at getting another "newer" not necessarily new iMac that you can tweak to do what you want. Especially if you are interested in Linux. The only other alternative you have is to pay top dollar for a current model Mac.
I don't think your existing iMac is saveable, it sounds like several things could be wrong with it and at 12 years old, well, that's not surprising.

Not a bad idea to buy something newer-but-not-new. If I were determined to pair Linux with Mac at all costs, that'd be the way to go. As it happens we've spoken about getting one of the new Mac Minis if indeed the iMac is totally dead. Something up to date, easy to hide behind the external screen we'd already got. Could be a thing.

One thing that I didn't read that you had tried is to zap the PRAM. To do this you should have a wired Mac keyboard and hold down the Command Option P and R keys as soon as you hit power. Then let the 4 keys go after you hear a 3rd chime. At that point you should be able to hold down the Option key to get to the boot menu.

As far as OCLP goes, you can use it to install a newer OS (Big Sur or Monterey), but I wouldnt go up to anything newer than that on a 2012 Mac. If you do install OCLP, you may want to isntall the drivers on both the inetral and external drive. These get installed by the software on the EFI partition.

You can always try to install Linux on the external drive, but this is not something that I have ever done, I have always installed it on internal drives. I am not sure if anything is needed to boot from linux on an external. This may be dependent on what flavor bistro that you use.

I think my nvram reset attempts amount to the same thing? Does a wired keyboard functionally matter/change anything if the wireless keyboard does in fact seem to register key input? Regardless, I gave it another go (with my wireless keyboard, mind), and still no dice. After the third chime I let go, tried for the boot menu... nope.

Fair idea to try installing Linux on the SSD and then boot from it. Am I right in thinking that for a normal working Mac, if the only drives connected upon startup are an empty internal HDD and an external SSD with a working Linux distro... it should automatically try to boot from the SSD?

 

[MacsBug]

Your thinking is sound as far as if the internal drive does not have an OS on it that the computer will see an OS on an external SSD. But I believe this is only true if the OS is a version of the Mac OS. You may need to select the linux drive to boot from it from the boot manager. I do not believe that you can do this without getting to the boot screen,

One thing to note is that there is a CR2032 battery in your iMac that may be dead, and this could be the reason that you are getting the white screen.

here are the instructions on how to replace it. iMac Intel 21.5" EMC 2389 PRAM Battery Replacement Just note that its not an easy process.

 

[Gene Jacket]

Your thinking is sound as far as if the internal drive does not have an OS on it that the computer will see an OS on an external SSD. But I believe this is only true if the OS is a version of the Mac OS. You may need to select the linux drive to boot from it from the boot manager. I do not believe that you can do this without getting to the boot screen.

Fair point, good to know. I haven't got MacOS installed on a drive (not counting the SSD), but I did try an Install MacOS image that didn't seem to register.

One thing to note is that there is a CR2032 battery in your iMac that may be dead, and this could be the reason that you are getting the white screen.

here are the instructions on how to replace it. iMac Intel 21.5" EMC 2389 PRAM Battery Replacement Just note that its not an easy process.

Haha, wow. That is incredibly involved for such a small thing. I don't know if I'd trust myself not to break anything else on the way to replacing the battery.