External Hard Drives Crash iMac


Hello everyone! I’ve posted before about my iMac crashing. You all advised to reseat all my ram. I wound up installing each stick at a time, making sure the machine was stable for a few days before adding the next. And it worked! Thanks for your help!

Now I have a new challenge - it seems that any time I attach an external hard drive that does not have a power source, it crashes my iMac.

I have an 8TB seagate hard drive that requires and ac adaptor that is always plugged into the iMac that works fine. But whenever I plug in my various WD external hard drives, or ones I’ve created using hard drive enclosures, I’ll leave my Mac running in the morning and coming back to it shut off with the message that my computer shut down unexpectedly on startup.

Has anyone experienced this? I’m running an iMac late 2015 27 in. With 64 GB Ram (3rd party - owc)


Are you plugging in multiple drives at a time? Or are you plugging in the 8TB drive AND only one other external drive (presumably powered by the USB port itself)? Why are you leaving this system “running in the morning”? Are you doing extensive disk operations throughout the process? Or are the drives just plugged in (with no activity)?

I’d have to wonder whether this is a hardware failure or a software conflict failure. Isolating which case it is requires may require a systematic approach to the troubleshooting.



Hi JJW -

The 8TB hard drive (w. power supply) is always plugged into the iMac.

The crash occurs whether it’s one additional external hard drive (powered by USB) or 2 or more. And I’ve witnessed it while I’ve been working on the machine. I’ll be working on it and it randomly shuts down.

If no external hard drives (powered by USB) are connected, the iMac always stays on.

I’m not doing anything extensive. I have Backblaze running on my computer, but I have not indicated to back up anything other than the 8TB drive. I have Plex server running on one of the external hard drives, but even when that is not connected and another external hard drive is, it shuts down the iMac.

I’m open to any approach to additional troubleshooting, thanks!


Last night, I actually connected a thunderbolt dock to the iMac and tried connecting one of the USB powered external hard drives, and a few minutes later, the machine crashed.


Is the Thunderbolt dock powered?


Yes, it’s the earlier version of this one: https://www.belkin.com/us/p/P-F4U085/


Use a powered USB port…sorted the issue for me. I think your drawing to much current.


That would have been my first guess, but the fact that it happened with the Thunderbolt dock (which should be powering the USB ports on the dock from its​ own wall plug) makes me think this may be some sort of software issue.


I also had this USB Hub Plugged into the computer, but didn’t have anything connected to it.

Not sure if it draws power, even when nothing’s connected, but I’ve removed it and plugged one of the USB powered external hard drives into the computer. If it crashes again, I will provide the Error Report.

Thanks everyone for the help so far!


Welp, that didn’t take long…Shut down after 20 min. of it plugged in. here’s the error report:

Anonymous UUID:       557C4138-1FCD-2215-612C-3426FBDCE502

Sat Nov 10 14:13:50 2018

*** Panic Report ***
panic(cpu 0 caller 0xffffff80190d84dd): Kernel trap at 0xffffff80190ba84f, type 6=invalid opcode, registers:
CR0: 0x0000000080010033, CR2: 0x000000011f6ed000, CR3: 0x0000000020712000, CR4: 0x00000000003626e0
RAX: 0xffffff80190ba84f, RBX: 0x0000000000000001, RCX: 0x000000000000003b, RDX: 0xffffff80a93c5d90
RSP: 0xffffff87206e9d80, RBP: 0xffffff87206e9db0, RSI: 0x0000000000000001, RDI: 0xffffff87206e9d90
R8:  0xffffff7f998b7950, R9:  0x0000000000000000, R10: 0xffffff7f998b7950, R11: 0x0000000000000000
R12: 0xffffff80190c8fd4, R13: 0x0000000000000005, R14: 0xffffff87206e9d8f, R15: 0xffffff7f998b7950
RFL: 0x0000000000010083, RIP: 0xffffff80190ba84f, CS:  0x0000000000000008, SS:  0x0000000000000010
Fault CR2: 0x000000011f6ed000, Error code: 0x0000000000000000, Fault CPU: 0x0, PL: 1, VF: 0

Backtrace (CPU 0), Frame : Return Address
0xffffff87206e9850 : 0xffffff8018faca9d 
0xffffff87206e98a0 : 0xffffff80190e6893 
0xffffff87206e98e0 : 0xffffff80190d82ba 
0xffffff87206e9950 : 0xffffff8018f59ca0 
0xffffff87206e9970 : 0xffffff8018fac4b7 
0xffffff87206e9a90 : 0xffffff8018fac303 
0xffffff87206e9b00 : 0xffffff80190d84dd 
0xffffff87206e9c70 : 0xffffff8018f59ca0 
0xffffff87206e9c90 : 0xffffff80190ba84f 
0xffffff87206e9db0 : 0xffffff80190d8292 
0xffffff87206e9e20 : 0xffffff8018f59ca0 
0xffffff87206e9e40 : 0xffffff7f998b7950 
0xffffff87206e9f50 : 0xffffff7f9b9a6aa5 
0xffffff87206e9f70 : 0xffffff80190d7a6c 
0xffffff87206e9fd0 : 0xffffff8018f59e4d 
0xffffffa77f9b3f30 : 0xffffff8018fcc0f7 
0xffffffa77f9b3f80 : 0xffffff8018fcc780 
0xffffffa77f9b3fa0 : 0xffffff8018f590ce 
      Kernel Extensions in backtrace:
            dependency: com.apple.iokit.IOACPIFamily(1.4)[DC1D9290-BFFC-309B-8529-CCB7AB322B1C]@0xffffff7f99e3f000
            dependency: com.apple.iokit.IOPCIFamily(2.9)[7DE930EC-AB73-3F5A-9D38-94D5EE90D197]@0xffffff7f99895000
            dependency: com.apple.driver.AppleSMC(3.1.9)[CE000030-3AC9-3E7E-8F53-9E8E34EE631A]@0xffffff7f99e48000

BSD process name corresponding to current thread: kernel_task

Mac OS version:

Kernel version:
Darwin Kernel Version 18.2.0: Fri Oct  5 19:41:49 PDT 2018; root:xnu-4903.221.2~2/RELEASE_X86_64
Kernel UUID: 5D53F7E4-472A-369D-97D8-4DD877A4BDFF
Kernel slide:     0x0000000018c00000
Kernel text base: 0xffffff8018e00000
__HIB  text base: 0xffffff8018d00000
System model name: iMac17,1 (Mac-DB15BD556843C820)

System uptime in nanoseconds: 1242310556789
last loaded kext at 251057500062: com.apple.filesystems.msdosfs	1.10 (addr 0xffffff7f9fc7b000, size 69632)
loaded kexts:
com.apple.filesystems.msdosfs	1.10
com.apple.driver.AppleTopCaseHIDEventDriver	138.2
com.apple.fileutil	1
com.apple.filesystems.autofs	3.0
com.apple.driver.AGPM	110.23.46
com.apple.driver.ApplePlatformEnabler	2.7.0d0
com.apple.driver.X86PlatformShim	1.0.0
com.apple.driver.AppleMikeyHIDDriver	131
com.apple.driver.AppleMikeyDriver	282.10
com.apple.driver.AppleUpstreamUserClient	3.6.5
com.apple.kext.AMDFramebuffer	2.0.2
com.apple.kext.AMDRadeonX4000	2.0.2
com.apple.driver.AppleHDAHardwareConfigDriver	282.10
com.apple.driver.AppleGraphicsDevicePolicy	3.25.6
com.apple.driver.AppleHDA	282.10
com.apple.AGDCPluginDisplayMetrics	3.25.6
com.apple.driver.AppleHV	1
com.apple.iokit.IOUserEthernet	1.0.1
com.apple.driver.AGDCBacklightControl	3.25.6
com.apple.driver.AppleBacklight	170.12.11
com.apple.driver.AppleIntelSKLGraphics	12.0.2
com.apple.iokit.IOBluetoothSerialManager	6.0.9f2
com.apple.driver.pmtelemetry	1
com.apple.Dont_Steal_Mac_OS_X	7.0.0
com.apple.driver.AudioAUUC	1.70
com.apple.driver.AppleMCCSControl	1.5.6
com.apple.driver.AppleIntelPCHPMC	2.0.1
com.apple.driver.eficheck	1
com.apple.driver.AppleSMCLMU	212
com.apple.driver.ACPI_SMC_PlatformPlugin	1.0.0
com.apple.kext.AMD7000Controller	2.0.2
com.apple.driver.AppleIntelSKLGraphicsFramebuffer	12.0.2
com.apple.iokit.BroadcomBluetooth20703USBTransport	6.0.9f2
com.apple.driver.AppleOSXWatchdog	1
com.apple.driver.AppleFIVRDriver	4.1.0
com.apple.driver.AppleIntelSlowAdaptiveClocking	4.0.0
com.apple.driver.AppleThunderboltIP	3.1.2
com.apple.iokit.SCSITaskUserClient	408.200.1
com.apple.iokit.IOBluetoothUSBDFU	6.0.9f2
com.apple.driver.AppleFileSystemDriver	3.0.1
com.apple.driver.AppleVirtIO	2.0.9
com.apple.filesystems.hfs.kext	407.200.4
com.apple.AppleFSCompression.AppleFSCompressionTypeDataless	1.0.0d1
com.apple.BootCache	40
com.apple.AppleFSCompression.AppleFSCompressionTypeZlib	1.0.0
com.apple.AppleSystemPolicy	1.0
com.apple.driver.AppleFWOHCI	5.6.0
com.apple.iokit.AppleBCM5701Ethernet	10.3.3
com.apple.driver.AppleSDXC	1.7.6
com.apple.driver.AirPort.BrcmNIC	1400.1.1
com.apple.filesystems.apfs	945.220.38
com.apple.driver.AppleAHCIPort	329.200.2
com.apple.private.KextAudit	1.0
com.apple.driver.AppleRTC	2.0
com.apple.driver.AppleACPIButtons	6.1
com.apple.driver.AppleHPET	1.8
com.apple.driver.AppleSMBIOS	2.1
com.apple.driver.AppleACPIEC	6.1
com.apple.driver.AppleAPIC	1.7
com.apple.nke.applicationfirewall	190
com.apple.security.TMSafetyNet	8
com.apple.driver.AppleActuatorDriver	2410.5
com.apple.driver.AppleHIDKeyboard	208
com.apple.driver.AppleMultitouchDriver	2410.5
com.apple.driver.AppleInputDeviceSupport	2410.2
com.apple.driver.AppleHSBluetoothDriver	138.2
com.apple.driver.IOBluetoothHIDDriver	6.0.9f2
com.apple.kext.triggers	1.0
com.apple.iokit.IOFireWireIP	2.3.0
com.apple.kext.AMDRadeonX4030HWLibs	1.0
com.apple.kext.AMDRadeonX4000HWServices	2.0.2
com.apple.driver.AppleGraphicsControl	3.25.6
com.apple.driver.DspFuncLib	282.10
com.apple.kext.OSvKernDSPLib	527
com.apple.iokit.IOAVBFamily	710.1
com.apple.plugin.IOgPTPPlugin	700.7
com.apple.driver.AppleSSE	1.0
com.apple.driver.AppleBacklightExpert	1.1.0
com.apple.iokit.IONDRVSupport	530
com.apple.driver.AppleSMBusController	1.0.18d1
com.apple.AppleGPUWrangler	3.25.6
com.apple.driver.IOPlatformPluginLegacy	1.0.0
com.apple.driver.X86PlatformPlugin	1.0.0
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com.apple.kext.AMDSupport	2.0.2
com.apple.AppleGraphicsDeviceControl	3.25.6
com.apple.iokit.IOAcceleratorFamily2	400.27
com.apple.iokit.IOSurface	255.1
com.apple.driver.AppleHDAController	282.10
com.apple.iokit.IOGraphicsFamily	530.12
com.apple.iokit.IOHDAFamily	282.10
com.apple.iokit.BroadcomBluetoothHostControllerUSBTransport	6.0.9f2
com.apple.iokit.IOBluetoothHostControllerUSBTransport	6.0.9f2
com.apple.iokit.IOBluetoothHostControllerTransport	6.0.9f2
com.apple.iokit.IOBluetoothFamily	6.0.9f2
com.apple.driver.AppleSMBusPCI	1.0.14d1
com.apple.iokit.IOSlowAdaptiveClockingFamily	1.0.0
com.apple.driver.AppleThunderboltEDMSink	4.2.0
com.apple.driver.AppleUSBAudio	315.6
com.apple.driver.usb.IOUSBHostHIDDevice	1.2
com.apple.iokit.IOAudioFamily	206.5
com.apple.vecLib.kext	1.2.0
com.apple.driver.usb.cdc	5.0.0
com.apple.driver.usb.networking	5.0.0
com.apple.driver.usb.AppleUSBHostCompositeDevice	1.2
com.apple.driver.AppleThunderboltDPInAdapter	5.5.8
com.apple.driver.AppleThunderboltDPOutAdapter	5.5.8
com.apple.driver.AppleThunderboltDPAdapterFamily	5.5.8
com.apple.driver.AppleThunderboltPCIUpAdapter	2.1.4
com.apple.driver.AppleThunderboltPCIDownAdapter	2.1.4
com.apple.driver.usb.AppleUSBHub	1.2
com.apple.iokit.IOSerialFamily	11
com.apple.filesystems.hfs.encodings.kext	1
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com.apple.driver.AppleIntelLpssGspi	3.0.60
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Model: iMac17,1, BootROM, 4 processors, Intel Core i5, 3.2 GHz, 64 GB, SMC 2.33f10
Graphics: AMD Radeon R9 M390, AMD Radeon R9 M390, PCIe
Memory Module: BANK 0/DIMM0, 16 GB, DDR3, 1867 MHz, 0x00, -
Memory Module: BANK 0/DIMM1, 16 GB, DDR3, 1867 MHz, 0x00, -
Memory Module: BANK 1/DIMM0, 16 GB, DDR3, 1867 MHz, 0x00, -
Memory Module: BANK 1/DIMM1, 16 GB, DDR3, 1867 MHz, 0x00, -
AirPort: spairport_wireless_card_type_airport_extreme (0x14E4, 0x14A), Broadcom BCM43xx 1.0 ( AirPortDriverBrcmNIC-1305.2)
Bluetooth: Version 6.0.9f2, 3 services, 27 devices, 1 incoming serial ports
Network Service: Wi-Fi, AirPort, en1
PCI Card: pci1b73,1100, USB eXtensible Host Controller, Thunderbolt@196,0,0
PCI Card: Broadcom 57762-A1, Ethernet Controller, Thunderbolt@194,0,0
PCI Card: pci11c1,5901, IEEE 1394 Open HCI, Thunderbolt@195,0,0
Serial ATA Device: APPLE HDD ST1000DM003, 1 TB
USB Device: USB 3.0 Bus
USB Device: External USB 3.0
USB Device: Backup+ Hub
USB Device: Backup+ Hub WH
USB Device: Bluetooth USB Host Controller
USB Device: FaceTime HD Camera (Built-in)
USB Device: Backup+ Hub
USB Device: USB 3.0 Bus
USB Device: USB PnP Sound Device
Thunderbolt Bus: iMac, Apple Inc., 28.1
Thunderbolt Device: Express Dock, Belkin International, Inc., 3, 26.2


Unfortunately, I suspect there’s something wrong with your USB bus hardware-wise.


May be worth reinstalling macOS as a troubleshooting step to rule something weird going on in the operating system before looking into a repair.


So I wound up taking it into the Apple Store. They reviewed the crash logs and ran tests, but could not pinpoint any issue with the hardware but saw that the crash’s may have had to do with GPU (weird). They suggested to reformat the computer entirely and add applications one by one.

I did this, and it turns out it is Carbon Copy Cloner that is causing the shut downs. I had 5 external hard drives plugged in with no problem and the moment I installed CCC, the shutdowns began again.


Huh. I would reach out to their support if your copy of CCC wasn’t updated. They are generally very good to work with.


Thanks for the follow-up. I’ll keep that in mind if I start having any similar issues. I went from many years of SuperDuper! to CCC in 2016, and so far it’s been golden. Hopefully that gold won’t tarnish.


Not sure CCC would be causing your shutdown,maybe the power draw from the attached drives. Are the on a powered USB hub?


After months of frustration, I reached out to OWC and explained the issues I was having. They were insistent that it wasn’t the RAM, but they sent me a replacement set and said if the new set of RAM worked fine, I could return the original sticks.

Turns out that this has solved all of my issues of external hard drive shutting down the system, random restarting, everything.

I am able to plug in all of my multiple external hard drives and run CCC with no issues at all.

I feel like I have a new/reliable machine!