Mojave Security Update 2021-004 result in Blinking Folder with Question Mark

New cables for Power and USB Drives. Same results but for the 4th time in 4 days...

1. Wait for the infamous flashing folder
2. Switch off the iMac from mains (equal to pull the cable off)
3. Count 10/15 seconds
4. switch on the mains (equal to attach the iMac power cable)
5. Count 5 seconds
6. switch the iMac on.
7. it boots

It looks like I'm on a failed Boot to SMC reset - Good Boot cycle here and it's something I cannot understand.

Well,

Less nonsense actually.

1. Boot : Cold boot minutes after a shutdown or a night of being switched off (and the power strip as well)
2. Flashing Folder with "?"
3. Switch off by pressing the power button (long press)
4. immediately after shutdown, switch on by pressing the power button (short press)
5. Boot ok.

This happened three times yesterday.

I have noticed that when the boot fails the USB enclosure light of the SSD is on but it does not flash for data reads since power on. When the boot will be a good one, the USB enclosure light of the SSD is on and flashes for data reads.

If the FW Drive is on even the cold boot 'reads' the drive and tries to boot from my Time Machine backup. (TB1 to FW Apple Adapter). This points me to think I am observing an USB failure at cold boot. If I unplug all USB devices the message is the same Flashing Folder, so at cold boot having the USB SSD boot drive plugged does not make a difference. I need to check if all ports are affected or only the one were the USB SSD Boot is plugged is.

USB ports current output looks good (the drive enclosure lights up) but no data. So I have the 5V but I might not have the Amperes to have a data read when cold boot (Electrical problem) but if that would be the case how can it be that at warm boot all is normal and stays perfect for hours of operation ? I could point to a capacitor but it would have been broken by now. Well it might be that an electrical problem occurred during Firmware writing and some damage was inflicted to SMC controller / logic board components so that the problem is now permanent. An SMC reset after a boot failure usually fix it.

That's why now that I think I have isolated the problem (USB) it's likely to be a logical problem in the boot sequence. This might come from firmware or SMC.

Macs can boot from TB or USB. The newer M1 Macs (MacBook Air, MacBook Pro) have TB ports only.

I think the security update is a back port from Big Sur and newer Macs.

I can state that because the Startup Disk Icon at boot when pressing ALT are the ones in the new M1 Macs, not the usual ones.

My point is that a Security Update cannot break the electrical components but can contain a firmware with a bug so that the logical boot sequence is altered and does not take into account USB Drives at Cold Boot but only at Warm Boot due to NVRAM / SMC reading it afterwards.

Or... the NVRAM CMOS battery passed away exactly when I was doing the security update, which is an incredible coincidence.

So candidates :

• Electrical Problem
• NVRAM CMOS Battery gone
• Firmware boot sequence altered

Cast your vote.

Thanks so far,

Pasha.

Thank you.

I have discovered a strange thing, kind of weird but it I was able to make it happen twice.

1. Wait for the infamous flashing folder
2. Switch off the iMac from mains (equal to pull the cable off)
3. Count 10 seconds
4. switch on the mains (equal to attach the iMac power cable)
5. Count 5 seconds
6. switch the iMac on.
7. it boots

If this happens again and again I can tell it's SMC as the above procedure it's the same as SMC reset but without unplugging the power cord from the iMac (it is plugged into a power strip with a switch).

In any case case points to something that looks reproducible.

Any thoughts?

I think a software update cannot break a PSU. Likely Logic Board firmware gone. Google reports that possibility. A logic board swap likely fixes it. I made a burn in test. The machine stays up for 10h without loosing a beat. So once it boots it is rock stable. That’s why I think PSU is less likely but it cannot be excluded.

The problem is that I cannot move to a new M1 Mac until my DAW is native and that will happen by end of the year.

Thanks. It happens to humans as well. You have a stomach pain and you think it's last thing you ate.

Maybe it's what you ate a day beforeand youforgot about it.

Sure the firmware was updated during Mojave Update 2021-004 (I opened up the package and it contains a firmware update), that could stress the components on the electrical side. In a nutshell, it can be that simply iMac is ageing and I got caught in a mere coincidence. So far the second boot is always the good one, if done within 15 seconds after the last shutdown. Boring but it works.

Thanks.

I confirm:

1. I can see all boot drives from Sys Prefs>Startup Disk
2. I can select the Boot Drive and Restart
3. Restart ends in Flashing Folder and Question mark
4. My only OS is Mojave
5. My machine does not support Big Sure
6. Catalina is the highest I can afford
7. an USB Drive with Catalina is not able to boot automatically as well

Thanks a lot for help

Cheers

Paolo

I am not aware on any ground issues, however all was working fine and it broke 'during' the Security update so I assume it was the cause. In any case, good point I will investigate with fresh cables.

Thanks!

Thanks a lot for supporting me. I really appreciate that.

Your insight is precious for me.

This morning following your hint I made another set of tests.

Well, I confirm the odd behaviour of Power On, Get the Folder. Switch Off. Power Again (with 10 seconds + 5 Seconds Delay) and it starts normally.

I discharged the capacitors as suggested by pressing the Power Button when power strip was off.

Then I started with Power Button Pressed long and fans were running like a 777 at take off.

Then the same power off, wait 10, power strip on, wait 5, power on... and worked.

The illness is not cured but now I am trying to do the math.

Let's say that it's not the PSU but very close. It's electric. Who holds the data about the Boot drive? NVRAM. That NVRAM should be sustained by a CMOS battery and maybe SMC as well (that holds critical info about the machine as well as disks).

So if I power on and I got the Folder with "?" then I switch the power strip off, then back again ( When iMac is connected to power it drains current even if it is off. You can tell by the current lighting up my FW Audio) iMac can actually sustain the data in the NVRAM if I make it quick enough to avoid full discharge of PSU capacitors or residual current.

So my take is that the Data about 'self' is not there at cold boot. When booting after a failure by following the SMC reset procedure it might be that such 'almost warm' boot can retain the info. To me this looks elcetrical or should I say Digital Data corruption. It's not the SSD boot drive as this behaviour does not change if I change it with a fresh copy of Catalina. Maybe during Firmware writing something went wrong and now NVRAM holds corrupt data forever.

So thanks for making my grey cells thinking about... what if it's not software... The data in the firmare, the data in the volatile RAM is the 'sense of self' in iMac. If that is corrupted you cannot boot. There are chains of events that renew and protect that data from being lost, as I do with my odd power cycle. So PSU is involved and capacitors might be as well.

Am I on the wrong path?

Thanks!

Thanks. My requirements are limited. I do not use multi layered sampled libraries nor video edit at 4K. Occasionally 2K footage. Ableton Live Suite I use never triggered swap in 8 years. 8GB will be fine to me. I record audio files, sound comes from Guitar, Bass and external MIDI Modules plus Zebra2 Synth (not sampled). To me 8GB will be enough. I will check used with 16GB as well.

Thanks for this.

Keep in mind I do not have macOS on the internal drive.

Done. Here's the results:

1. Disconnect all USB Devices except the SSD USB Drive. Boot Ok **
2. Did your procedure twice
3. on try 1 got Flashing Folder and "?"
4. Switch it off
5. leave it alone for 15 minutes
6. on try 2 got Flashing Folder and "?"
7. Switch it off
8. Switch it on and boot. Boot Ok

It's becoming nonsense to me. Now gotta backup some data then I will power cycle again and report.

Thanks

Pasha

** started from there as it was a test I never did before and you brought in the idea.