MacBook Pro showing the "prohibited" symbol screen on almost every boot up after upgrading to High Sierra

Question

MacBook Pro showing the "prohibited" symbol screen on almost every boot up after upgrading to High Sierra

I have recently bought a used MacBook Pro. I will try and give as many relevant details as possible. If any more are needed, please let me know.

MacBook Pro 13" (mid 2012)

10GB RAM (added)

250GB SSD

2.5GHz dual-core Intel Core i5 processor (original)

... remaing specs are also original

After installing (attempting to) High Sierra, I have faced issues with the "prohibited" symbol. However, after trying a lot of different things like formatting the ssd, clearing NVRAM, resetting SMC so on. Finally I was able to boot up in safe mode and set up an account.

Unfortunately, when rebooting normally, the "prohibited" symbol was showing again after entering the password to my newly created account. After trying this a couple of times (shutting down using the power button and rebooting), I was finally able to boot the OS perfectly. I have no problems once I have booted up correctly.

I am probably able too boot up without any errors 1/10 times (at best). It is always the "prohibited" symbol that is displayed when I can't boot up.

Also, I think it is worth mentioning, that the MacBook is making a strange noise when I press the power button and I starts up. The sound is a lot like the one in this youtube video:

P1150671.MOV - YouTube

Well, I think I gave as many details as possible for the moment. If you need anything else, please let me know.

Any help will be greatly appreciated.

MacBook Pro, OS X Mountain Lion (10.8.5), to High Sierra

Posted on Jun 13, 2018 12:41 PM

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Answer 1

Jun 14, 2018 4:57 AM in response to madslangkilde

Hi again

I tried running a hardware diagnose by pressing "d" when booting. I didn't find any errors, but I was able to se the distribution of the RAM's. I guess these are dedicated to different cores. As shown in the image, one of them has only 2 GB, while the other one has 8 GB.

Could the cause of the issue be that it boots up using a core with insufficient RAM for this particular OS (High Sierra). Because Mountain Lion had no problems booting up.

I have never replaced RAM's myself, nor moved them around. But is it possible to give each core 5 GB of RAM? Or how would you allocate these?

In any case, I think I shold watch some youtube videos before actually doing it.

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Answer 2

John Galt

Level 10

147,162 points

Jun 14, 2018 1:42 AM in response to madslangkilde

The "prohibited" symbol means the Mac can't find a startup disk. Resetting NVRAM is the correct thing do to, but you did that already.

10 GB RAM is not original, nor is that configuration a supported one. That's the first big clue. Try removing the additional 2 GB, or replacing the original RAM.

EtreCheck may help provide additional relevant details: Using EtreCheck

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Answer 3

Barney-15E

Level 10

117,142 points

Jun 14, 2018 1:42 AM in response to madslangkilde

A prohibitory symbol means it cannot find necessary boot files.

https://support.apple.com/en-us/HT204156

If you can boot into safe mode, that seems contadictory, but it could be something you had installed previously that has borked the OS. Safe Mode may disable what is preventing it finding the system folder.

I think John Galt may be on the right track with the RAM.

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Answer 4

John Galt

Level 10

147,162 points

Jun 14, 2018 6:37 PM in response to madslangkilde

Please refer to MacBook Pro: How to remove or install memory - Apple Support.

Your model MacBook Pro supports a maximum 8 GB RAM. Unsupported configurations will result in unexpected effects.

The DIMMs (memory modules) installed in that Mac permit a configuration of either 2 or 8 GB. Either one or both of them can be causing the intermittent failure to boot, or the problem may be entirely unrelated. Diagnosing it requires removing one or the other, or (preferably) replacing either or both DIMMs with memory verified to meet Apple's stringent specifications.

Having purchased that Mac "used" makes it difficult for you to determine that RAM's provenance. Either module may have been included when it was built, but both is quite impossible.

My recommendation is to revert to known, unequivocally supported configuration and go from there.

Post the EtreCheck report if you would like assistance with it.

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Answer 5

Jun 14, 2018 1:36 AM in response to John Galt

Hello @John Galt

Thanks a lot for your help. I tried resetting the NVRAM again, but still without any luck.

I will attempt removing 2 GB of the RAM as a last resort.

EtreCheck didn't give anything relevant (unfortunately).

I will get back to you if I figure something out.

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Answer 6

Jun 14, 2018 1:41 AM in response to Barney-15E

Hello @Barney-15E

Thanks a lot for your help so far.

I don't really know what should be installed previously that could have an impact on this. And besides, I didn't really install anything after buying it from the previous owner and it seemed like it was cleaned completely. Also, I reinstalled and wiped it afterwards.

As for the safe mode, I think it may have been a coincidence the last time. I tried doing it again a couple of times, but this time it displayed the "prohibited" symbol as when booting normally. Safe mode is accessed by holding "shift" when booting, right?

I look forward to hearing from you again

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Answer 7

Barney-15E

Level 10

117,142 points

Jun 14, 2018 10:23 AM in response to madslangkilde

The only sound I heard in that video was the optical disk drive--normal if you have one.

If you are only getting a normal boot ⅒ times, I would suspect the problem might be related to the startup drive being corrupt, failing, or something similar.

You need to boot into Recovery, Run First Aid on the drive, then reinstall the OS.

The RAM isn't assigned to cores or cpu's. You have two banks with a single DIMM.

Depending on the Mac, it may run better if the RAM is paired (i.e. same type, speed, size) in the two banks, but that's not the problem with boot up.

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MacBook Pro showing the "prohibited" symbol screen on almost every boot up after upgrading to High Sierra

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