APC Back-UPS USB Connection is Causing OS X to Hang at Startup...

After installing 10.11.3 my iMac27 went back to cold booting and restarting without problem. A couple of weeks later, the boot failure happened again - and the failure was repeatable. This was after I had removed all other USB external drives (only Thunderbolt external drives were connected). I have disconnected the APS UPS USB cable and the boot failure has gone away. I will leave it disconnected until 10.11.4 comes out, and will see if the problem is fixed.

I agree that this is pretty strange behavior.

David

I am also having the same problem with my Cyberpower CP15000PFCLCD hanging at progress bar when restarting. Remove USB cable and no problem restarting. I think this is due to a sleep issue because if I shut down and start the computer it does not happen. If I just restart after it has been but to sleep everyday for a week it will hang.

Exactly the opposite for me. My system has no problems waking from sleep - but fails to boot in a start from power off or a restart if the APS USB cable is connected. I have the UPS cable disconnected now and have no problems re-booting the system.

David

Since a reset of SMC I have not had the system hang at restarting at the Apple logo. So I hope it is fixed.

This doesn't help on my iMac27 Retina. I reset the SMC (by powering off and disconnecting the power cord for 15 seconds) - and after plugging back in the APS USB cable, restarting fails with a hang about half-way through (as before). I don't think this is a solution to the problem for everyone. One thing I have noticed is that sometimes this seems to fix the problem, but after a while, the failures start again.

David

Ugh, not good news. I have applied the OS X update and will reconnect the cable and see what happens after a reboot. I don't expect this will fix the issue.

I understand that Apple now has a Twitter support account - I am not a Twitter user, but was thinking about signing up just so I could send this issue to Apple. Apparently, they are providing individual support. My Bug Report to Apple has generated no response at all - which, I understand, is not unusual.

Again, Ugh.....

David

I just tried it - I reconnected the UPS USB cable and rebooted. The boot hung like always. Clearly, the bug has not been corrected by Apple. I disconnected the UPS USB cable, and the system booted without problems. Again, Ugh.

David

Just noticed this issue as well. After this recent update I am having this same problem. Mine seems to be caused by my Caldigit Thunderbolt Station. Can not finish a boot sequence until it has been unplugged. Did not have this issue the last 3-4 weeks when I first added this device, but now after the update I am in the same boat as you guys seem to be.

One of the odd things about this bug is that it appears to be intermittent. I went through several weeks in which my system booted without problem with the UPS USB cable connected - then it started failing again, and now consistently fails on my iMac 27 Retina system. I have another iMac 21.5 with the UPS USB cable connected and it doesn't seem to have any problems booting. But then, that system only has one external USB drive connected. My Retina system has three Thunderbolt external drives and one USB 3 external drive connected. That complexity is associated with the problem, I think.

David

How is the battery condition on the APS USB backup for the 27"? There has been a few times in my career where I have not been able to restore a system due to having a faulty APS unit, even though it shows as being good. Have you tried switching the APS units to see if the problem follows?

It's an almost new unit - and shows 100% charge when the USB monitoring cable is connected. I haven't tried disconnecting the power to make sure it will be able to power the system, but I am confident it would. I haven't had a power failure here in ages - all our utilities are underground, and NV Energy is very reliable. The only reason to have the USB cable connected is so that you can program system behavior in the event of a power failure - but I don't leave my systems powered on when I am not present - I put them into sleep mode - so that is not a critical issue. If the power fails when I am present, I can manually power down the system. Power is off completely when I am away from the systems for more than a day. The APS brand units really lets you know when the battery will no longer hold a charge - I had that happen on another unit that was four years old.

It is just irritating that this function - behavior during a power failure, which is built-in on OS X - doesn't work. On Windows, there is a separate program you can run - but I think Win 10 now handles this internally in the OS.

David

Solved!!! Disable Power Nap and all works fine (boot, ups shut down, charge, etc.)

iMac Retina 5k late 2014 with APC SmartUPS 750i

Mac mini late 2014 with APC SmartUPS 750i.

Nope - disabling Power Nap makes no difference - the boot still hangs in the same place with the APS data cable connected. This is with the 10.11.5 update installed.

David

Ah, ****. I was hoping they'd finally fix it with 10.11.5

I'm not sure if it's just the UPS, or if it involves the whole USB stack

(which they apparently rewrote in 10.11)