fresh install on SSD for MacPro5,1 boots sometimes OK, sometimes prohibitory symbol

Question

fresh install on SSD for MacPro5,1 boots sometimes OK, sometimes prohibitory symbol

Hardware: Two nearly identical MacPro5,1 ("Mid-2010" and "Mid-2012")

I'd like to upgrade them to an SSD. The latest OS that these machines can run is High Sierra, which is OK for what I'd like to do with them.

After installing a firmware update, I can update the original HDD to High Sierra. This works OK.

I can also install it to the SSD without obvious errors. It then boots into the fresh install without problems. A reboot, however, often gives the prohibitory symbol.

This happens on both Mac Pros. I'm fairly good with identifying software and hardware problems, but this leaves me at a loss. I've tried resetting PRAM and NVRAM and booting into safe and verbose modes.

The SSD is formatted with AFPS, and also has a separate partition for Linux. Does it have to do with how the SSD is partitioned? (Can't say I got my head around how AFPS volumes work). I'm grateful for any tips.

Mac Pro

Posted on Aug 3, 2022 12:48 AM

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Answer 1

Aug 3, 2022 9:47 AM in response to BDAqua

Yes.

I've also tried another older SSD, which works fine.

Maybe it's this brand-new SSD that's the problem? It's a fairly standard Samsung 870 EVO 500 GB SATA 2,5".

The SSD is partitioned into two: One partition is currently exFAT (will later be Linux/ext4) and another is the AFPS container, in which there is currently one AFPS volume. I could try next to reformat the entire disk to only hold an AFPS container and nothing else.

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Answer 2

Aug 4, 2022 1:44 AM in response to BDAqua

Thanks! That link was very helpful. That explains the strange on-and-off problems. So it seems it was indeed an SSD that was too new, and Apple never bothered to upgrade its drivers. I'm ordering a Crucial SSD now that is reported to work well.

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