Serial Crashes - iMac 2017


Hi, Apple Support Community!

Thank you for your superb service and continued support!

I have a 2017 iMac, which would sporadically crash. I keep it up-to-date using the latest MacOS (BigSur). I have also run disk utility's first aid from within the system. Since Sept. 2020, my iMac has been crashing frequently - once every few days, or a few times a day. I have already had to reinstall the MacOS (and my files), as well as run virus checks (Avira and Avast). I have also saved most of the reports generated by the computer upon crashing (with the latest one pasted below). Finally, I have run the disk utility using the MacOS Recovery instructions provided by Apple and the result is that there is no hardware problem/issues. So, having spent countless hours trying to have my computer working normally without crashes, I've decided to reach out to you and see if you might be able to figure out what the real issue is and how to solve it.

Thank you in advance for taking the time to help out!

Have a wonderful weekend!



(a Mac fan since 1993)

The Latest Crash Report

panic(cpu 3 caller 0xffffff801436ea25): userspace watchdog timeout: no successful checkins from in 120 seconds

service returned not alive with context : unresponsive dispatch queue(s):

service:, total successful checkins since volume unfreeze notification (78941 seconds ago): 7883, last successful checkin: 120 seconds ago

service:, total successful checkins since volume unfreeze notification (78941 seconds ago): 7895, last successful checkin: 0 seconds ago

Backtrace (CPU 3), Frame : Return Address

0xffffffa0c23e3670 : 0xffffff80110b9aed

0xffffffa0c23e36c0 : 0xffffff80111fc6e3

0xffffffa0c23e3700 : 0xffffff80111ecd1a

0xffffffa0c23e3750 : 0xffffff801105ea2f

0xffffffa0c23e3770 : 0xffffff80110b938d

0xffffffa0c23e3890 : 0xffffff80110b9678

0xffffffa0c23e3900 : 0xffffff80118be434

0xffffffa0c23e3970 : 0xffffff801436ea25

0xffffffa0c23e3980 : 0xffffff801436e678

0xffffffa0c23e39a0 : 0xffffff801184569e

0xffffffa0c23e39f0 : 0xffffff801436dab4

0xffffffa0c23e3b20 : 0xffffff801184f86b

0xffffffa0c23e3c80 : 0xffffff80111a7d81

0xffffffa0c23e3d90 : 0xffffff80110bf0e7

0xffffffa0c23e3e00 : 0xffffff8011095905

0xffffffa0c23e3e60 : 0xffffff80110ad012

0xffffffa0c23e3ef0 : 0xffffff80111d0ec3

0xffffffa0c23e3fa0 : 0xffffff801105f216

Kernel Extensions in backtrace:[7AE04EA4-D026-39A0-B2D5-5C9E4EE72967]@0xffffff801436d000->0xffffff801436efff

Process name corresponding to current thread: watchdogd

Mac OS version:


Kernel version:

Darwin Kernel Version 20.2.0: Wed Dec 2 20:39:59 PST 2020; root:xnu-7195.60.75~1/RELEASE_X86_64

Kernel UUID: 82E2050C-5936-3D24-AD3B-EC4EC5C09E11

KernelCache slide: 0x0000000010e00000

KernelCache base: 0xffffff8011000000

Kernel slide: 0x0000000010e10000

Kernel text base: 0xffffff8011010000

__HIB text base: 0xffffff8010f00000

System model name: iMac18,2 (Mac-77F17D7DA9285301)

System shutdown begun: NO

Panic diags file available: YES (0x0)

Hibernation exit count: 0

System uptime in nanoseconds: 164821627575409

Last Sleep: absolute base_tsc base_nano

Uptime : 0x000095e786901ecf

Sleep : 0x000032a44bfd329a 0x000000009c795164 0x00003295220bcd4d

Wake : 0x000032a45075672e 0x000000009c3aad08 0x000032a44f566669

last started kext at 150016478199764: >usb.!UUserHCI 1 (addr 0xffffff7fb199d000, size 98304)

last stopped kext at 127805235975653: >usb.!UUserHCI 1 (addr 0xffffff7fb199d000, size 98304)

loaded kexts:

>usb.!UUserHCI 1

>!ATopCaseHIDEventDriver 4020.6

>AudioAUUC 1.70

>AGPM 119

>!APlatformEnabler 2.7.0d0

>X86PlatformShim 1.0.0

>!AUpstreamUserClient 3.6.8

@fileutil 20.036.15

@kext.AMDFramebuffer 4.0.2

@filesystems.autofs 3.0

@kext.AMDRadeonX4000 4.0.2

>!A!IKBLGraphics 16.0.1

@kext.AMDRadeonServiceManager 4.0.2

>!AHDA 283.15

>!A!IPCHPMC 2.0.1

>!A!IKBLGraphicsFramebuffer 16.0.1

@kext.AMD9500!C 4.0.2

>!AGraphicsDevicePolicy 6.2.2

@AGDCPluginDisplayMetrics 6.2.2

>eficheck 1

>pmtelemetry 1

>LuaHardwareAccess 1.0.16

|IOUserEthernet 1.0.1

|IO!BSerialManager 8.0.2f9

@Dont_Steal_Mac_OS_X 7.0.0

>!AHV 1

|Broadcom!B20703USBTransport 8.0.2f9


>!AGFXHDA 100.1.431

>!ADiskImages2 1

>!AThunderboltIP 4.0.3

>!A!ISlowAdaptiveClocking 4.0.0

>!AMCCSControl 1.14

@filesystems.tmpfs 1

@filesystems.hfs.kext 556.60.1

@BootCache 40

@!AFSCompression.!AFSCompressionTypeZlib 1.0.0

@!AFSCompression.!AFSCompressionTypeDataless 1.0.0d1

@filesystems.apfs 1677.60.23

>!ASDXC 1.9.0

|!ABCM5701Ethernet 11.0.0

>AirPort.BrcmNIC 1400.1.1

>!AAHCIPort 346

@private.KextAudit 1.0

>!AACPIButtons 6.1

>!ARTC 2.0



>!AAPIC 1.7

@!ASystemPolicy 2.0.0

@nke.applicationfirewall 310

|IOKitRegistryCompatibility 1

|EndpointSecurity 1

>!AHIDKeyboard 222

>!AMultitouchDriver 4400.28

>!AInputDeviceSupport 4400.35

>!AHS!BDriver 4020.6

>IO!BHIDDriver 8.0.2f9

@kext.triggers 1.0

@kext.AMDRadeonX4200HWLibs 1.0

@kext.AMDRadeonX4000HWServices 4.0.2

>DspFuncLib 283.15

@kext.OSvKernDSPLib 529

|IOAccelerator!F2 439.52

@kext.AMDSupport 4.0.2

>X86PlatformPlugin 1.0.0

>IOPlatformPlugin!F 6.0.0d8

>!AGraphicsControl 6.2.2

>!ASMBusPCI 1.0.14d1

|IOSerial!F 11

|IOAVB!F 900.12

@plugin.IOgPTPPlugin 900.11

|IOEthernetAVB!C 1.1.0

|Broadcom!BHost!CUSBTransport 8.0.2f9

|IO!BHost!CUSBTransport 8.0.2f9

|IO!BHost!CTransport 8.0.2f9

>!AHDA!C 283.15

|IOHDA!F 283.15

|IONDRVSupport 585

|IOAudio!F 300.6.1

@vecLib.kext 1.2.0

@!AGPUWrangler 6.2.2

@!AGraphicsDeviceControl 6.2.2

|IOSlowAdaptiveClocking!F 1.0.0

|IOGraphics!F 585

>!ASMBus!C 1.0.18d1

>usb.networking 5.0.0

>usb.!UHostCompositeDevice 1.2

>!AThunderboltDPInAdapter 8.1.4

>!AThunderboltDPAdapter!F 8.1.4

>!AThunderboltPCIDownAdapter 4.1.1

>!AHPM 3.4.4

>!A!ILpssI2C!C 3.0.60

>!A!ILpssI2C 3.0.60

>!A!ILpssDmac 3.0.60

>!ABSDKextStarter 3

|IOSurface 289.3

@filesystems.hfs.encodings.kext 1

|IOAHCIBlock!S 332

|IO80211!F 1200.12.2b1

|IOSkywalk!F 1

>mDNSOffloadUserClient 1.0.1b8

>corecapture 1.0.4


|IONVMe!F 2.1.0

>!AThunderboltNHI 7.2.8

|IOThunderbolt!F 9.3.2

>usb.!UXHCIPCI 1.2

>usb.!UXHCI 1.2

|IOUSB!F 900.4.2


>!AEFIRuntime 2.1

|IOSMBus!F 1.1

|IOHID!F 2.0.0

$!AImage4 3.0.0

|IOTimeSync!F 900.11

|IONetworking!F 3.4

>DiskImages 493.0.0

|IO!B!F 8.0.2f9

|IOReport!F 47

|IO!BPacketLogger 8.0.2f9

$quarantine 4

$sandbox 300.0

@kext.!AMatch 1.0.0d1

|CoreAnalytics!F 1

>!ASSE 1.0

>!AKeyStore 2

>!UTDM 511.60.2

|IOUSBMass!SDriver 184.40.6

|IOSCSIBlockCommandsDevice 436.40.6

|IO!S!F 2.1

|IOSCSIArchitectureModel!F 436.40.6

>!AMobileFileIntegrity 1.0.5

@kext.CoreTrust 1

>!AFDEKeyStore 28.30

>!AEffaceable!S 1.0

>!ACredentialManager 1.0

>KernelRelayHost 1

|IOUSBHost!F 1.2

>!UHostMergeProperties 1.2

>usb.!UCommon 1.0

>!ABusPower!C 1.0

>!ASEPManager 1.0.1

>IOSlaveProcessor 1

>!AACPIPlatform 6.1

>!ASMC 3.1.9

|IOPCI!F 2.9


>watchdog 1

@kec.pthread 1

@kec.corecrypto 11.1

@kec.Libm 1


In Geostationary Orbit
Yes you are running a 2017 Intel Mac but if you had an M1I would say a reinstall! ;)

please tell us what Mac OS X are you running because the answer could come quicker!


OP post says near the top that he is running Big Sur. The log shows build 20C69, so macOS 11.1

@lambreff: Were you already using Big Sur (beta) when this started happening?
Big Sur seems less stable for some, so you COULD try updating to the current 11.2 release version.
Are the crashes completely random (it could be the result of anything?) - or, do you get crashes most often when you are doing a particular task?
It can be worthwhile to keep an informal log, to note how long your Mac has been running when you get a crash, and something about the circumstances (what are you doing at that moment?)


What software is running right before the crash?
Hi Cheryl,
It happens with all kinds of applications running.

So, it’s occurred multiple times over many months. I’m always running all kinds of applications.

Hope that helps.

Thank you and I look forward to hearing from you.


Do you remember if the problem started before you upgraded to Big Sur?
Have you run Diagnostics , not just the Disk Utility? You start the built-in Diagnostics by restarting while holding the letter D, or Option-D. Either should work.

Does your iMac have a fusion drive, or a "real" SSD, or the 1 TB spinning/slow standard hard drive?

How much RAM is installed?

Have you upgraded any part of the hardware, such as adding more RAM?
You can actually upgrade up to 64GB, but the procedure requires major disassembly of your iMac - and is a clearly non-trivial task - but maybe you have done that (?)


Rosie Moderator
Staff member
So, it’s occurred multiple times over many months. I’m always running all kinds of applications.
It would help if you tell us what app (s) are running or your using when the crash occurs. As Delta suggested start a handwritten log of what you are doing, what you have running just before the crash.

It is possible that you are running an app that can not run properly on Big Sur and needs an upgrade/update. It could be as simple as a printer driver needs to be updated.