Prohibitory Conundrum

[eyoungren]

So here's a question. Why do I get a prohibitory symbol on boot when I use an SSD, but not with a mechanical hard drive?

Background…

Old SSD worked fine under High Sierra. Got my two new GPU cards, which allowed me to update my MP to Mojave. Did fine for a short while. I even updated. MP was running just fine when I got my first Cinema Display. That meant a shutdown. Once everything was hooked up, the Mac boots with a prohibitory symbol.

Messed around quite a bit, finally cloned from a week old backup (which started something else). In order to do the clone, I had to reinstall Mojave onto an internal drive that had the space. It was only AFTER I did this install that I realized I had used dosdude's Mojave patcher.

Some notes at this point. • Booting and trying to reinstall Mojave from the recovery volume I ran into graphic glitches and the Mojave on the recovery volume refused to install because it said I had no Metal-compatible cards. • After cloning to the spinner I was able to boot no problem.

Continuing on, I put this down to the SSD I had. So, I ordered a new one, double the size (1TB). But I wasn't totally trusting of the new SSD.

The new SSD has for the most part worked, but there have been a couple of times where I still ran into the prohibitory symbol. A boot from the recovery drive and using Disk Utility First Aid fixed that.

Until today, when I rebooted on purpose to try and repair font caches. As I expected, I got the prohibitory symbol. I've spent about an hour and a half trying various things (cloning to a spinner again was my final resort).

Again, I tried to reinstall Mojave from the recovery drive and got told I didn't have any Metal compatible cards. So, I installed it from the USB drive again that has dosdudes Mojave patcher.

Booted right up off the SSD and all is functioning normally.

I have no idea why the system would still tell me I have no Metal compatible GPUs. I also don't know what's going on behind the scenes using the patcher to install Mojave to a system that can already support it.

I can only speculate that because my GPUs are flashed, this is the culprit. But why would it work on a spinning HD and not an SSD?

 

[B S Magnet]

So here's a question. Why do I get a prohibitory symbol on boot when I use an SSD, but not with a mechanical hard drive?

Background…

Old SSD worked fine under High Sierra. Got my two new GPU cards, which allowed me to update my MP to Mojave. Did fine for a short while. I even updated. MP was running just fine when I got my first Cinema Display. That meant a shutdown. Once everything was hooked up, the Mac boots with a prohibitory symbol.

Messed around quite a bit, finally cloned from a week old backup (which started something else). In order to do the clone, I had to reinstall Mojave onto an internal drive that had the space. It was only AFTER I did this install that I realized I had used dosdude's Mojave patcher.

Some notes at this point. • Booting and trying to reinstall Mojave from the recovery volume I ran into graphic glitches and the Mojave on the recovery volume refused to install because it said I had no Metal-compatible cards. • After cloning to the spinner I was able to boot no problem.

Continuing on, I put this down to the SSD I had. So, I ordered a new one, double the size (1TB). But I wasn't totally trusting of the new SSD.

The new SSD has for the most part worked, but there have been a couple of times where I still ran into the prohibitory symbol. A boot from the recovery drive and using Disk Utility First Aid fixed that.

Until today, when I rebooted on purpose to try and repair font caches. As I expected, I got the prohibitory symbol. I've spent about an hour and a half trying various things (cloning to a spinner again was my final resort).

Again, I tried to reinstall Mojave from the recovery drive and got told I didn't have any Metal compatible cards. So, I installed it from the USB drive again that has dosdudes Mojave patcher.

Booted right up off the SSD and all is functioning normally.

I have no idea why the system would still tell me I have no Metal compatible GPUs. I also don't know what's going on behind the scenes using the patcher to install Mojave to a system that can already support it.

I can only speculate that because my GPUs are flashed, this is the culprit. But why would it work on a spinning HD and not an SSD?

By default, I’m guessing you run verbose boot on the MP, yes? I’m curious what it might display when a boot-up process is successful.

 

[eyoungren]

By default, I’m guessing you run verbose boot on the MP, yes? I’m curious what it might display when a boot-up process is successful.

Ahem…I used to.

But I have not now for quite some time and stupid me, I didn't think to try that at any point in this process.

It's all booting/running well now (because I reinstalled Mojave from the patched USB stick) of course so the problem is gone.

 

[m1maverick]

Isn't the prohibitory symbol an indication that you need to enter a firmware password? Perhaps the Mojave patcher combined with the non-metal GPUs is doing something to affect the EFI making the Mac think a firmware password is set?

 

[Amethyst1]

Isn't the prohibitory symbol an indication that you need to enter a firmware password?

I think that makes a lock show up on the screen with a text field asking for the password. The prohibitory symbol can mean "unsupported machine" or other problems - e.g. I get that when trying to boot OS X via USB on my 2007 MBP for some reason.

 

[eyoungren]

Isn't the prohibitory symbol an indication that you need to enter a firmware password? Perhaps the Mojave patcher combined with the non-metal GPUs is doing something to affect the EFI making the Mac think a firmware password is set?

I've not heard of it occurring in this manner. I might buy it though, if:

• It happened on a spinning hard drive. It doesn't
• It happened shortly after the Mac started to boot. It happens about two thirds of the way through the boot process.
• It didn't randomly choose to boot from the SSD.

None of this was a problem under High Sierra. That said, I had three stock Apple cards for my displays then. The new GPUs are flashed (as I mentioned).

In my limited research this apparently was a bug with early or beta versions of Mojave. The solution was to boot from recovery and repair the HD. That's worked a few times, but not this time around.

 

[m1maverick]

I think that makes a lock show up on the screen with a text field asking for the password. The prohibitory symbol can mean "unsupported machine" or other problems - e.g. I get that when trying to boot OS X via USB on my 2007 MBP for some reason.

Ah, that's right. Thanks for clearing up my confusion.

 

[TheShortTimer]

I think that makes a lock show up on the screen with a text field asking for the password. The prohibitory symbol can mean "unsupported machine" or other problems - e.g. I get that when trying to boot OS X via USB on my 2007 MBP for some reason.

Yeah, I received the prohibitory symbol whilst attempting to install Panther of all things via USB on an iMac G3, which was really strange.

 

[Amethyst1]

Yeah, I received the prohibitory symbol whilst attempting to install Panther of all things via USB on an iMac G3, which was really strange.

Possibly means "cannot access the device I'm supposed to boot from" - I don't think Panther supports booting from USB.

 

[Yebubbleman]

Isn't the prohibitory symbol an indication that you need to enter a firmware password? Perhaps the Mojave patcher combined with the non-metal GPUs is doing something to affect the EFI making the Mac think a firmware password is set?

I think that makes a lock show up on the screen with a text field asking for the password. The prohibitory symbol can mean "unsupported machine" or other problems - e.g. I get that when trying to boot OS X via USB on my 2007 MBP for some reason.

Yeah, I received the prohibitory symbol whilst attempting to install Panther of all things via USB on an iMac G3, which was really strange.

Possibly means "cannot access the device I'm supposed to boot from" - I don't think Panther supports booting from USB.

FYI: The Prohibitory symbol means that it can't load the kernel that you are trying to boot. Common causes of this are trying to load an OS that wasn't meant for that particular system (such as a system-specific "gray disc" build of Mac OS X, an older version of Mac OS X than that system was originally introduced, or a non-gray-disc version of the gray-disc version that shipped with that system - the common thread between all of them is lack of driver support for that particular Mac in the version of Mac OS X that you are trying to run on it) and/or not having proper kernel extensions/drivers for your hardware to be able to boot the operating system. You can try booting in safe mode.

It's possible that the OP's storage/SATA controller doesn't have a driver that knows what to do with an SSD. Though, I'm thinking that this isn't terribly likely, since a new enough OS is being used and it's not like 2.5" SATA SSD's really change things dramatically at a SATA level.