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Unable to access Recovery Partition on 27" late 2015 iMac under Big Sur

C

cromagnontech

macrumors member
Original poster
Sep 16, 2014
34
7
In Big Sur, on my late 2015 27" Retina iMac, I can no longer access the Recovery Partition via Cmd-R (it only launches the Internet version of Recovery, and then moves into El Capitan era version of Recovery / Disk Utility etc, as El Cap was the original OS on this machine). I've tried the following:

- clearing NVRAM and SMC reset
- rolling the machine all the way back to El Cap, then installing Big Sur from there

The recovery partition is listed in terminal if I type 'diskutil list'.

When El Cap was installed, the local recovery partition was fully accessible under Cmd-R.

I'm actively working with Apple techs on the issue, but wondered if anyone else is having the issue, and, if so, which iMac you have? (Mine is also one of the iMacs that is stuck on the 170.0.0.0 firmware as per another thread here - I'm also wondering if these are connected).
 
cromagnontech said:
In Big Sur, on my late 2015 27" Retina iMac, I can no longer access the Recovery Partition via Cmd-R (it only launches the Internet version of Recovery, and then moves into El Capitan era version of Recovery / Disk Utility etc, as El Cap was the original OS on this machine). I've tried the following:

- clearing NVRAM and SMC reset
- rolling the machine all the way back to El Cap, then installing Big Sur from there

The recovery partition is listed in terminal if I type 'diskutil list'.

When El Cap was installed, the local recovery partition was fully accessible under Cmd-R.

I'm actively working with Apple techs on the issue, but wondered if anyone else is having the issue, and, if so, which iMac you have? (Mine is also one of the iMacs that is stuck on the 170.0.0.0 firmware as per another thread here - I'm also wondering if these are connected).
Click to expand...
I have exactly the same issue. Exactly.

Same model, same firmware.

The recovery partition in Big Sur appears in diskutil list, but CMD-R brings up internet recovery for El Capitan. OPT-CMD-R gives me an error code (-5101F).

I've even tried the same troubleshooting steps to no avail. I even tried reinstalling via USB install media.

What's the thing about the firmware version? I'll have a read up of that.
 
micbarry said:
I have exactly the same issue. Exactly.

Same model, same firmware.

The recovery partition in Big Sur appears in diskutil list, but CMD-R brings up internet recovery for El Capitan. OPT-CMD-R gives me an error code (-5101F).

I've even tried the same troubleshooting steps to no avail. I even tried reinstalling via USB install media.

What's the thing about the firmware version? I'll have a read up of that.
Click to expand...
That's really helpful to know, many thanks for sharing. I also get the -5101f with Cmd-Opt-R at reboot.

Here's a thread on the firmware issue - https://forums.macrumors.com/thread...te-2015-efi-firmware-update-failures.2228324/. It appears that people have managed to resolve it by installing a whole new internal hard drive ... pretty drastic, when the SSD in my iMac appears to be otherwise fine.

Would also be helpful to know if people WITH updated firmware (e.g. 428.0.0.0.0, which I believe is the correct, current firmware), can access Recovery Mode OK?
 
Another data point...my girlfriend has the same model at work. The difference is that it has a spinning hard drive rather than an SSD. It's on 428.0.0.0.0. It was on Mojave at one point, but was rolled back to High Sierra by her IT department.

The only other difference is that her machine has OEM RAM whereas mine has RAM from OWC.

I think it has more to do with the SSD than the type of RAM by the sounds of things.

It would be interesting to update her machine to Big Sur to see if it boots into recovery, but I'm not sure if I can take responsibility for that.
 
micbarry said:
Another data point...my girlfriend has the same model at work. The difference is that it has a spinning hard drive rather than an SSD. It's on 428.0.0.0.0. It was on Mojave at one point, but was rolled back to High Sierra by her IT department.

The only other difference is that her machine has OEM RAM whereas mine has RAM from OWC.

I think it has more to do with the SSD than the type of RAM by the sounds of things.

It would be interesting to update her machine to Big Sur to see if it boots into recovery, but I'm not sure if I can take responsibility for that.
Click to expand...
Yes, the working theory is that something related to the SSD model is preventing or blocking the firmware upgrades beyond 170.0.0.0.0. Whether that is also connected to the Recovery issue in Big Sur is not clear, but certainly seems plausible. Maybe, if it is, it will finally force Apple's hand in resolving the firmware issue.
 
Hopefully, someone will join in with confirmation that they have the same model with upgraded firmware that can boot into recovery.

As a workaround, I'll be keeping a USB installer on hand if I need to boot into recovery for any reason. Not super elegant, but it works.
 
Last edited:
micbarry said:
Hopefully, someone will join in with confirmation that they have the same model with upgraded firmware that can boot into recovery.

As a workaround, I'll be keeping a USB installer on hand if I need to boot into recovery for any reason. Not super elegant, but it works.
Click to expand...
Yes, hopefully. Please folks, if you're reading this, please add to this data on whether Recovery is working, and what your firmware version is.
 
I have the late-2015 27" iMac. I am still running Mojave, but I have the updated firmware (428.0.0.0.0). I just tried and was successfully able to boot into Recovery mode.

Edit: If it matters, I have the model with a 2 Terabyte Fusion drive.
 
An update: I have taken the liberty of posting a comment on this thread:

eclecticlight.co

What is responsible for persistent firmware update failures?

Following a survey of 37 iMac17,1 systems, there’s no evidence problems are caused by hardware. It’s most likely to be a bug in the firmware installer.
eclecticlight.co eclecticlight.co

They are aware of the firmware issue there, but not yet quite aware (with the exception of one commenter) about not being able to boot into the recovery partition in Big Sur. Interestingly, that person is on firmware version 173.0.0.0.0.

Please note that as of this posting, my comment is awaiting moderation, and thus may not appear immediately.
 
cromagnontech said:
That's really helpful to know, many thanks for sharing. I also get the -5101f with Cmd-Opt-R at reboot.

Here's a thread on the firmware issue - https://forums.macrumors.com/thread...te-2015-efi-firmware-update-failures.2228324/. It appears that people have managed to resolve it by installing a whole new internal hard drive ... pretty drastic, when the SSD in my iMac appears to be otherwise fine.

Would also be helpful to know if people WITH updated firmware (e.g. 428.0.0.0.0, which I believe is the correct, current firmware), can access Recovery Mode OK?
Click to expand...
Deleted
 
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ThugFreak said:
I have the same 27'' iMac (late 2015). It has an OWC SSD in it. It has some other brand of ram (not OWC). It originally had 170.0.0.0 firmware. When I installed Catalina, the firmware changed to 176.0.0.0
Then I went back to Mojave. I have the same problem with the recovery partition with the new firmware, but I use bootable USB installer drives , so it doesn't affect me. Does 428.0.0.0 come with Big Sur?
Click to expand...
428.0.0.0.0 comes prior to Big Sur, although I'm not sure where. My girlfriend's late 2015 iMac has this firmware, and she's never had Big Sur on that machine, so I know it isn't Big Sur, but I don't know at what point the firmware is supposed to go to 428.0.0.0.0.

May I ask which MacOS version were you running when you had issues with the recovery partition? Thanks!
 
RLRabb said:
I have the late-2015 27" iMac. I am still running Mojave, but I have the updated firmware (428.0.0.0.0). I just tried and was successfully able to boot into Recovery mode.

Edit: If it matters, I have the model with a 2 Terabyte Fusion drive.
Click to expand...
Are you able to post here once you update to Big Sur? On that firmware, I'd be interested if you can boot into the Big Sur recovery partition. Thanks!
 
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micbarry said:
428.0.0.0.0 comes prior to Big Sur, although I'm not sure where. My girlfriend's late 2015 iMac has this firmware, and she's never had Big Sur on that machine, so I know it isn't Big Sur, but I don't know at what point the firmware is supposed to go to 428.0.0.0.0.

May I ask which MacOS version were you running when you had issues with the recovery partition? Thanks!
Click to expand...
Deleted
 
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ThugFreak said:
I was on Mojave. It didn't work on High Sierra either. I didn't try it on Catalina, since I was only on that for a few hours. I don't install updates. Maybe 428.0.0.0.0 comes from there.
Click to expand...
Yes - I suspect it is either Mojave or Catalina.
 
Thanks for all of your contributions. It appears to be a bit of a mixed bag. On my machine, stuck on 170.0.0.0.0, it was able to access Recovery on Catalina and Mojave, but is not able to on Big Sur. It has the original 512GB SSD in it.

We do need to bear in mind that the Recovery Partition issue may be completely unconnected to the firmware not updating; it may just be a bug in Big Sur affecting iMac 2015" 27" machines. I haven't seen anyone in this thread confirm that they have a) installed Big Sur, b) have 428.0.0.0.0 AND c) can access the Recovery partition.

(I believe that 428.0.0.0.0 was part of one of a later Catalina point releases BTW: maybe 10.15.5 or 10.15.6?)
 
ThugFreak said:
I have the same 27'' iMac (late 2015). It has an OWC SSD in it. It has some other brand of ram (not OWC). It originally had 170.0.0.0 firmware. When I installed Catalina, the firmware changed to 176.0.0.0
Then I went back to Mojave. I have the same problem with the recovery partition with the new firmware, but I use bootable USB installer drives , so it doesn't affect me. Does 428.0.0.0 come with Big Sur?
Click to expand...
That's interesting, as it implies that a later firmware prevents an earlier version of the OS from accessing the Recovery Partition, and that there may therefore be a link between the firmware version and the ability to access it, albeit in the 'reverse' direction in your case compared to mine (old firmware with new OS, vs. newer firmware with older OS).
 
"(I believe that 428.0.0.0.0 was part of one of a later Catalina point releases BTW: maybe 10.15.5 or 10.15.6?)"

I have the 428 firmware and never installed Catalina or Big Sur.
 
RLRabb said:
"(I believe that 428.0.0.0.0 was part of one of a later Catalina point releases BTW: maybe 10.15.5 or 10.15.6?)"

I have the 428 firmware and never installed Catalina or Big Sur.
Click to expand...
It is probably Mojave, I'd say, that installs 428.
 
micbarry said:
It is probably Mojave, I'd say, that installs 428.
Click to expand...
I think 428 came out during the Catalina timeframe, but that security patches for Mojave (and maybe High Sierra?) released at the same time, also added it on the older OSes.
 
I was thinking that perhaps - if it is not related to firmware - that an update to Big Sur (11.1?) might fix the recovery mode issue. Could simply be a software issue.
 
micbarry said:
I was thinking that perhaps - if it is not related to firmware - that an update to Big Sur (11.1?) might fix the recovery mode issue. Could simply be a software issue.
Click to expand...
Maybe both.

Considering the symptoms of trying to boot into the various recovery modes, my best guess is the recovery partition is there, it just fails to boot because of firmware requirements. It simply is not compatible with the iMacs firmware level, which is at a much lower level than expected.

If Apple is aware of these firmware issues (must be) and they are not able to easily fix it (likely, or something would have happened in 3 years?) their fix could be to either a) ignore it and accept a significant amount of people are not able to boot into recovery mode or b) somehow fix the recovery volume to boot on this lower firmware level.

Of course, the best option would be if they can get these firmware updates restored, but I honestly think we would have seen that by now...
 
indy913 said:
Maybe both.

Considering the symptoms of trying to boot into the various recovery modes, my best guess is the recovery partition is there, it just fails to boot because of firmware requirements. It simply is not compatible with the iMacs firmware level, which is at a much lower level than expected.

If Apple is aware of these firmware issues (must be) and they are not able to easily fix it (likely, or something would have happened in 3 years?) their fix could be to either a) ignore it and accept a significant amount of people are not able to boot into recovery mode or b) somehow fix the recovery volume to boot on this lower firmware level.

Of course, the best option would be if they can get these firmware updates restored, but I honestly think we would have seen that by now...
Click to expand...
That's a good assessment. It's interesting that Apple now have a large number of customers who cannot boot into recovery. Perhaps until now, there was no 'good reason' to fix the firmware update issue, whereas now there's a very good reason.

I would find it hard to imagine that they would abandon 17,1 customers. They sold a lot of those!
 
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