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

Tried it again now that I've been on 10.11.5 for a while.

still hangs on cold boot.

😢

Experiencing the same issue; iMac hangs at about the 60% mark on the progress bar during booting up or restarting . I narrowed it down to my UPS connection. When I disconnect the UPS' USB cable it boots up instantly. The issue can be replicated every time. This is a recent phenomenon.

Tried all of the suggestions in this thread including changing USB ports, resetting NVRAM, SMC, toggling Power Nap, etc. with no change.

Once booted up I can reconnect the UPS' USB cable and the iMac works normally including recognizing the UPS.

This is not an issue when waking from sleep, only on booting up or restarting.

• iMac (27-inch, Late 2013)
• OS X 10.11.6 (15G31)
• CyberPower CP1000PFCLCD PFC Sinewave UPS

Yeah, it took me a while to figure it out.

Mine also, the problem is only at cold boot. never when waking from sleep or warm booting.

Had the problem originally with my APC UPS (which was pretty old) and so replaced it

and had the problem with my new CyberPower UPS.

The problem is definitely with El Capitan. I had no issues with Yosemite, then went directly to

El Cap 10.11.1 and have had problems since. I'm hoping that the issue is fixed in 10.12, but

even if it is I'm not sure whether an upgrade will be enough vs having to do a clean install.

As far as I can tell it has something to do with the USB stack as that's the last thing in the

logs before I have to forcibly power down and unplug the UPS cable. I've filed a bug report

with Apple but have never heard anything. I suspect that if I upgrade to 10.12 and it's not fixed

then I'll backup and clean install and see if that works.

• iMac 5k (27-inch, Late 2014)
• OS X 10.11.6 (15G31)
• CyberPower CP1000PFCLCD PFC Sinewave UPS

Indeed DrDuuude. I originally had an APC UPS with no problems.

However I didn't have this issue with the CyberPower UPS until fairly recently. I cannot be sure if it occurred with one of the most recent OS X v10.11x update(s) or not, but it seems likely.

I also filed a bug report with Apple and just sent a note to CyberPower as well.

Love the CyberPower UPS otherwise!

Hi Rich,

So your reply got me to revisit this whole issue from scratch. I once again unplugged all my USB devices.

In the past, plugging in the UPS would have it not boot. This time to my surprise, it booted fine.

Then once I plugged in the rest of my stuff it wouldn't boot.

Unplug the UPS - it boots.

Unplug everything except the UPS - it boots.

So I guess maybe the problem is either some weird conflict, or actually a problem with my other stuff.

So now I removed my USB hub, and extension cables, and plugged everything (mouse, 2 drives, UPS)

directly into the iMac, and switched my scanner (which was previously plugged into the hub) to wireless.

Now everything seems to work, and system preference energy save recognized my UPS model, which

it didn't before.

So maybe this is all related to either the usb hub or USB extension cables?

Both of these are known to generally cause problems.

Hope this helps with this frustrating (and solved?) problem.

Hey DrDuuude. So glad to hear that the issue's been resolved in your favor! Unfortunately, not so for me.

I have this Satechi USB Hub, an external SSD and an HDD dock attached directly to the iMac. Nothing's running through the hub however. I just use it with the odd thumb drive, etc. now and then.

I had tried booting up with nothing attached other than the CyberPower UPS a while back and I just gave it another try. Same result. It hangs at about 60%. It boots up immediately without the CyberPower connected, with or without other peripherals.

I can't positively say that it's the CyberPower UPS causing the issue. It could be how the iMac "communicates" with it. However it seems to be the culprit one way or another, at least for me.

The odd thing is that I've had the CyberPower UPS connected to the iMac for over a year and it's only been problematic fairly recently. Wish I could pinpoint when it started.

I haven't heard anything from CyberPower to date. Probably won't, but between Apple and CyberPower I hope this gets resolved. I don't reboot very often but it's a bit of a pain when I do.

Thanks for the update!

iMac (Retina 4K, 21.5 in, Late 2015), OS X 10.11.6

3.1 GHz Intel Core i5

16 GB 1867 MHz DDR3

1 Tb

LaCie 1 Tb ext HD

APC UPS BE 550G

Had booting problems: hang-ups with progress bar a lit over 50%; progress bar on one occasion turned into a white rectangle; on one occasion had a thin, multi-colored lightning bolt flash across the screen; and on a number of occasions the computer booted, and then there was a brief flash of an errorr msg with a stop sign that disappeared so quickly it could not be read.

Problem went away when when USB between iMac and UPS was disconnected.

Applecare says error msg is not an Apple msg. Not much help from APC rep.

Did have Bootcamp installed, and never had a problem when booting into Windows 10. (Have since wiped iMac clean, and reinstalled OS X only, but that's another story.)

Think I'll connect UPS USB cable after booting, and disconnect after powering down, until there is a fix.

I am brand new to this discussion because I just upgraded from Yosemite to El Capitan 10.11.6 and it took me nearly a half of a day to figure out it was the cable between my APC BACK-UPS R S 800 and my iMac 27 Mid-2010. Up until today all was well. So, I know have no UPS attached. And, I'm having this problem with the latest version of El Capitan.

I was having this problem with my late 2014 iMac with Yosemite and it took me a while to work out it was my CyberPower UPS. I could boot to Boot Camp then restart in OS X and it would boot every time so I presumed it was a Boot Camp problem. After a while the problem disappeared, that is until recently. I have been running El Capitan for a while but now even restarting from Boot Camp it would not boot. I unplugged all external devices and through a process of elimination worked out it was the UPS. For now I'm just running without the USB cable plugged in and this is alright if I'm home as I can shut down manually but I hope there is a permanent fix soon.

So are with Sierra I have not had a problem with it hanging on startup with my Cyberpower.

Yeah, after 2-3 months of no issues, I've once again started having boot problems with the UPS connected.

I've not seen any mention of this in the OS X release notes for each update.

I've filed a bug report with Apple, but as far as I know, no solution.

I haven't upgraded to 10.12.1 yet, still on 10.11.6

Hopefull Sierra will resolve this, but I'm not optimistic.