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Released June 2012 / Core i7 processor with Turbo Boost / Up to 1 GB DDR5 Video RAM

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Prohibitory sign after SSD Upgrade

Hey everyone,

First of all I have checked most of the answers people got with the same issue. Unfortunately nothing worked for me.

I have recently upgraded my HDD with a new SSD (WD Blue - 1TB 3D NAND) on my Macbook Pro 15” Mid 2012. The first thing I have tried was to connect my old HDD with an external adapter and restore the Mac Partition (High Sierra) on my new SSD. After it was finished it booted without a problem. I later decided to upgrade to MacOs Mojave, and I got the very first Prohibitory sign. It was loading up to certain point and was showing the prohibitory sign after a while.

Interestingly, when I installed the HDD back to the computer, it was booting perfectly. So I thought, maybe if I format it with the the new format I am not familiar with (APFS), it could work. But it didn’t. I also tried to clean install Mac Os Mojave to the new SSD but did not work.

I finally decided to install MacOS Mojave on the SSD and transfered everything from the old HDD with the migration assisstant. And it works perfectly with the external adapter. After a while my internal HDD also stopped working. I know get the same prohibitory sign with my old HDD with High Sierra.

So, I decided to replace the SATA cable, but it did not change anything. I still get the prohibitory sign on my SSD and HDD if the are internally connected. But they work if they are connected via external adapter.

Here are a few interesting details: I have a bootcamp partition on my HDD and Windows boots perfectly, internally or externally connected since the beginning.

I am almost sure the new cable is working fine, because my infrared receiver was not working anymore, and it works now with the new SATA cable.

I am beginning to think that this is really a problem about EFI or the new APFS format, which I know nothing about.

Any help would be appreciated. I am booting with an external for the last few weeks now.

Thank you..

Répondre à cette question J'ai le même problème

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Is the old drive an SSHD?


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While Apple states it supports 2012 MacBook Pro’s, I’m not sure if the Unibody was what they meant as there is the 2012 retina model as well. But, if you put that aside, I don’t recommend using High Sierra or Mojave on SATA based system with APFS as the queue depth is not very deep unlike PCIe/AHCI or PCIe/NVMe blade SSD’s used in the retina models.

So what to do here??

There are a few different versions of the HD SATA cable and you really need to newer one with a SSD drive. This has to do with the ability of the cable to handle the higher flow rates the SSD pushes and pull’s, unlike an HDD. The other factor is many people damage the cable just putting it in! Many people stress the cable when they fold it around the corners. In truth you want a even arch not a sharp fold as you damage the thin foil wires and the shield.

Here is the correct cable: MacBook Pro 15" Unibody (Mid 2012) Hard Drive Cable Apple P/N 923-0084. I also place a strip of electricians tape on the uppercase where the cable crosses over as the rough surface tends to wear the cable as well.

I would reformat the SSD and stick with Sierra. Once you get it working with it make a good backup (TimeMachine) just in case. Then give Mojave a try again. It you want to you can alter the installer not to upgrade the SSD to APFS file system.

Image MacBook Pro 15" Unibody (Mid 2012) Hard Drive Cable


MacBook Pro 15" Unibody (Mid 2012) Hard Drive Cable


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Thank you for the clarification. I bought a cable that says ¨Apple MacBook Pro 15" A1286 Unibody 2012 SATA HDD Cable 821-1492-A¨. And my model is A1286 (MacBookPro9,1)

Unfortunately the cable you have suggested is not sold in the ifixit Canada store.

So I will try to backup the partition and install it with the Mac OS Extended (Journaled) format. Do you know how to prevent the installer not to format it to APFS? I seriously believe that this could be the main problem because Windows is working just fine even as internal drive.

Thanks a lot..



I wanted to check if you gave this cable a try and if it solved your problem. I'm having a similar issue with a new Samsung 860 EVO SSD for a MacBook Pro 13" Unibody Mid 2012.

The thing that worries me is that the product description of the cable doesn't say anything about being compatible with the higher SSD's speeds as explained in this post: SSD doesn't boot properly..

Thanks and all the best!


@Juan - Life is so simple ;-} Apple doesn't fully explain things or their actions.

We know the original HD SATA cables used in the 2009 & 2011 models were designed for the HD drives of the time (SSD were just coming onto the market and still very expensive!) The drives at this time where only SATA II (3.0 Gb/s).

So lets think this though in a different way... A road built in 20's might not be suitable for a more modern car or truck, yet we drive on them as long as we don't exceed what it was designed to support. So you can't go too fast as the road might be too windy at higher speed or maybe the bridge is not able to support the weight of the truck or maybe the underpass is too low for the truck to go under without getting stuck.

SATA is like this! It has three versions SATA I (1.5 Gb/s), SATA II (3.0 Gb/s) & SATA III (6.0 Gb/s). So we can have a SATA I drive fit in any system, but we can't put in a fixed speed SATA III drive in a SATA I or SATA II system as the data rate is too much. While some SATA III drives are able to match up to the systems SATA port's limits many don't or might have a problem as the system port has an issue in the negotiation process.

So getting back to the cable, Apple used a newer PCH chip in the 2011 models but programmatically limited them to SATA II in the systems EFI code (BIOS) originally. It later enabled SATA III support but they had a problem! The cables they used just couldn't support SATA III data flows reliably! Hence the first update of the cable if someone upgraded their SATA II drive the system had to a faster SATA III drive that pushed the data flows harder in the 2011 models.

Later Apple had to move to SATA III drives as the supplier of the SATA II drives they where using no longer offered them. In the 2012 models Apple also improved the cable again as people where starting to push the SATA III interface even harder with high RPM HDD drives and then once more when SSD drives where pushing the interface even harder as the price while still expensive was becoming more common! Today a good SSD is about what people where paying for a good HDD back then.

So there in a nutshell is the history of the HD SATA cable.

As far as markings on the cable or what people list as its ability. I have not seen anyone state it as most people assume you would use the newest version of cable. Sadly, Apple didn't offer a newer parts listing for the 2011 models once the 2012 model came out so you need to use experience here to know what is transferable.

here's a bit more on the other thing you can face Your Hard Drive Cable Is A Ticking Time Bomb and even just putting in the cable can damage it if you are not careful! Many people crease the cable where it needs to go around a corner which damages it! You need to shape a nice arc in the cable as the sharp bend damages the thin foil wires within it. I use a BIC pen ink straw to help me form the radius.


@danj I know this post had been dormant for quite some time, but I am having the same issue on a Mid 2012 Macbook Pro 15" (a fun winter project). I understand the need to replace the SATA cable per your previous explanation.

Is the only difference between the original 2012 cable and the new replacement cable (as linked in your original response) the data rate limit? Since there are no "specs" listed on the product page, how would someone know that it can properly handle an SSD? I am not doubting you, as I just purchased it, but more wondering how this new cable is any better if its a direct replacement for the original one?


@Frank Cerny - What makes one thing better than another? The design and construction! That the same thing here.

The original cable was flawed to the extent it was only tested with the drives of the day - SATA II (3.0 Gb/s). SATA III (6.0 Gb/s) drives were still not real and even when they where Apple stayed with the older drives for quite awhile. Then to add to it HDD's still didn't leverage the full bandwidth of the newer SATA III spec. so early HD drives (high RPM) where rarely able to bump up against the 6.0 GB/s throughput. It was only when hybrid SSHD drives came out we started to see the cables start to be the issue.

Then SATA SSD's came out they started out slow but year to year they improved! Todays SSD's are now held back by the SATA III I/O limit! Todays high speed drives are M.2 based or custom (in the case of Apple) using still more effective I/O standards (PCIe/NVMe).

So getting back to your question! The cable is like your boat anchor chain how strong it is will determine if you boat floats away! Thats not an issue with the anchor or your boat the chain was the weak link. So the chain needs to be as strong as the they are if not more so. This is the same case here.


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You want to stay away from APFS in general, so format your internal drive into Mac OS Extended (Journaled), then try installing Mojave or HS onto your internal drive formatted into MOSEJ format and see if works with the drive scheme being MOSEJ instead of APFS.

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I tried that, but I think the installer reformatted it in APFS anyway before installing.


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Gurhan Gunay sera éternellement reconnaissant.
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