Mac Pro 2023 will not boot with PCIe SSD installed.

Me too. On my 2019 Mac Pro I had been using a 1TB 4M2 for the audio drive and 2TB 4M2 for the CCC backup.

I decided to double those values and do a 2TB 8M2 for the main audio drive and 4TB 4M2 for the CCC backup.

So, it's just kind of luck that I even had a 4TB 4M2 here to try as a last resort and notice that it worked.

I'll report back when I get the 2nd 4TB 4M2 which I hope is tomorrow. I'm going to put it right in and see if it works as my CCC backup to the 4TB 4M2 which which is currently working.

Some progress has been made. While for some reason, the new and unformatted OWC 8M2 drive was still causing this issue (it could be due to needing an additional power cable/supply), I tried a new and unformatted OWC 4M2 drive and it worked.

I am currently back to work using the M2 Mac Pro and a new OWC 4M2 PCIe SSD to store my active audio projects.

In talking with OWC, it seems that the new Mac Pro might not like external PCIe drives that are formatted to anything other than APFS Volume • APFS.

Hopefully Apple can release an update that makes the M2 Mac Pro work with a wider variety of external drives in terms of how they are formatted.

Just checking in here. My new OWC 4M2 that was purchased last week, the one that didn't prevent my Mac Pro 2023 from booting up when inserted, and was able to be formatted to APFS seems to be working great.

I've done a fair amount of work this weekend without an issue. For now I'm just using my 1TB OWC Envoy Pro mini (formatted to APFS as fate would have it) as my backup drive until my other new 4M2 arrives Tuesday. We'll see if that allows me to insert it without killing the Mac Pro 2023. Ideally that will be my backup audio drive that gets mounted every 15 minutes for Carbon Copy Cloner to back up the main audio drive and then eject the backup drive. That system worked great on my 2019 Mac Pro.

My older spinning 3.5" drives (used for older project archives) that are in my OWC Thunderbay 8 connected via Thunderbolt are also working just fine. I think those are SATA drives formatted to HFS.

I don't have time for this right now. It works with no PCIe cards, and with my 3 RME audio cards, and with my 3 RME audio cards and the 4TB OWC 4M2 PCIe SSD.

Something about the 4TB is allowing it to boot. Something about the 2TB is not allowing it to boot. The same was true with my 2TB 8M2 PCIe SSD.

Interesting stuff here. I'm not sure how the 4M2 units are formatted from OWC out of the box but both my new 2TB 4M2 and older and already formatted 1TB and 2TB 4M2 units definitely caused the issue.

My goal here is to have one large volume, and not a bunch of smaller volumes. I'm also not trying to reuse any of my older 4M2 SSDs at this point, I just need something that works.

The 4TB units are slighter large than one I need for my active projects (and backup) but I can't really invest any more time in this.

Something about the larger 4TB ones don't cause the issue, and I wouldn't be surprised if the 8TB and 16TB models work out of the box.

Something about the smaller sized ones and certain formatting types seem to be a trigger.

Hopefully Apple and/or OWC/SoftRAID will comment on this soon so we know what's going.

Even though I've had a solid working new M2 Mac Pro for over a week now, it's still slightly unsettling that a 10k Mac can just stop booting up due to a certain type of PCIe SSD inserted.

The PCIe slots for my audio cards and active project SSD(s) are a big part of why I went with this machine.

I got around the problem by using the new 4TB OWC drives that somehow didn't have this issue. I just installed 13.5 and everything still seems OK.

I really only wanted/needed a 2TB drive and 4TB backup but now I have two 4TB drives but it is what it is.

I do agree with the previous post that it's sad that Apple and OWC/Softraid just let this happen and it took this long for a supposed fix.

Apple send me a free pair of AirPod Pros that I didn't really need for all the HOURS of wasted time this posting on the forums, talking on the phone with them, sending videos, etc.

I would have preferred complimentary Apple Care or something more practical but it also is what it is.

It seems crazy that something as simple as a PCIe SSD could take down an entire computer like this did.

@SoftRAIDSupport

Thanks for the reply. Would this be true for brand new "Out of the Box" 42M drives that have never been formatted yet?

The problem is that since the Mac Pro 2023 won't boot at all with these 2TB drives inserted, I would have to use my old 2010 Mac Pro to do the formatting which I can do but...

If you didn't see my other messages. My 4TB 4M2 is for some reason working on "out of the box" in my 2023 Mac Pro. My brand new unformatted 2TB 8M2 and 4M2 would not allow the 2023 Mac Pro to boot up at all, which makes doing any formatting or SoftRAID changes impossible to do.

Attached is a screen shot of the 4TB 4M2 that out of the new box allowed the Mac Pro M2 to boot up and then I formatted and named it and has been fine since Friday.

I just tried another 2TB 4M2 out of the box (while the working 4TB remained in the Mac Pro) and it DID NOT allow the Mac Pro M2 to boot up.

I think I have logs from pressing SHIFT CONTROL OPTION COMMAND PERIOD KEY during the failed boots but I don't know where they are stored. I can find them you can point me to where they are.