Help with 27-inch iMac 2020, i9, 5700XT, 64 GB (Crash and Reboot)

[jshcy]

The iMac crashes suddenly while working on common tasks such as word processing (MS Word), e-mail (Outlook). I have not observed a particular pattern when those crashes occur. The only change I made to the iMac was to replace the Apple stock memory of two 4GB modules with 4 identical 16 GB modules of OWC memory. I'd appreciate any help with this.

Here is the latest report that I got after the latest reboot:

panic(cpu 13 caller 0xffffff801fc25c80): "Possible memory corruption: pmap_pv_remove(0xffffff80e1fc5bc0, 0x111c21000, 0xeca05e, 0xeca05e024, 0xffffff875a5dbc54, 0xfffffe9414851108): pv not on hash, head: 0xffffff80e1fc7ec0, 0x111c21000, priors: 2"@/AppleInternal/BuildRoot/Library/Caches/com.apple.xbs/Sources/xnu/xnu-6153.141.2.2/osfmk/i386/pmap_internal.h:979
Backtrace (CPU 13), Frame : Return Address
0xffffff875a5db8c0 : 0xffffff801fb1868d
0xffffff875a5db910 : 0xffffff801fc52ab5
0xffffff875a5db950 : 0xffffff801fc4463e
0xffffff875a5db9a0 : 0xffffff801fabea40
0xffffff875a5db9c0 : 0xffffff801fb17d57
0xffffff875a5dbac0 : 0xffffff801fb18147
0xffffff875a5dbb10 : 0xffffff80202bf2bc
0xffffff875a5dbb80 : 0xffffff801fc25c80
0xffffff875a5dbc80 : 0xffffff801fc25fa6
0xffffff875a5dbce0 : 0xffffff801fbb1c45
0xffffff875a5dbe30 : 0xffffff801fbb9571
0xffffff875a5dbe60 : 0xffffff801fb4948f
0xffffff875a5dbea0 : 0xffffff8020066878
0xffffff875a5dbf10 : 0xffffff8020066663
0xffffff875a5dbf30 : 0xffffff8020066639
0xffffff875a5dbf40 : 0xffffff8020182437
0xffffff875a5dbfa0 : 0xffffff801fabf206

BSD process name corresponding to current thread: com.apple.WebKit
Boot args: chunklist-security-epoch=0 -chunklist-no-rev2-dev

Mac OS version:
19H15

Kernel version:
Darwin Kernel Version 19.6.0: Thu Oct 29 22:56:45 PDT 2020; root:xnu-6153.141.2.2~1/RELEASE_X86_64
Kernel UUID: 9B5A7191-5B84-3990-8710-D9BD9273A8E5
Kernel slide: 0x000000001f800000
Kernel text base: 0xffffff801fa00000
__HIB text base: 0xffffff801f900000
System model name: iMac20,2 (Mac-AF89B6D9451A490B)
System shutdown begun: NO

System uptime in nanoseconds: 19271511323339
last loaded kext at 18167919320489: >!AXsanScheme 3 (addr 0xffffff7fa3a78000, size 32768)
last unloaded kext at 200882212106: >usb.!UHostPacketFilter 1.0 (addr 0xffffff7fa23f6000, size 24576)
loaded kexts:
com.getdropbox.dropbox.kext 1.13.0
com.paloaltonetworks.kext.pangpd 5.0.5f28
com.intel.driver.EnergyDriver 3.7.0
>!AUpstreamUserClient 3.6.8
>!ATopCaseHIDEventDriver 3430.1
@kext.AMDRadeonX6000 3.1.0
@kext.AMDRadeonServiceManager 3.1.0
>!AGraphicsDevicePolicy 5.2.6
@AGDCPluginDisplayMetrics 5.2.6
>!AHV 1
|IOUserEthernet 1.0.1
|IO!BSerialManager 7.0.6f7
>pmtelemetry 1
>AGPM 111.4.4
>!APlatformEnabler 2.7.0d0
>X86PlatformShim 1.0.0
@Dont_Steal_Mac_OS_X 7.0.0
>!A!IKBLGraphics 14.0.7
>!AThunderboltIP 3.1.4
>BridgeAudioCommunication 6.70.7
>!AHIDALSService 1
>!ABridgeAudio!C 6.70.7
>!AGFXHDA 100.1.429
>!A!ICFLGraphicsFramebuffer 14.0.7
>!A!IPCHPMC 2.0.1
>!AAVEBridge 6.1
>!A!ISlowAdaptiveClocking 4.0.0
>!AMCCSControl 1.14
@fileutil 20.036.15
@filesystems.autofs 3.0
>!UCardReader 489.120.1
>BCMWLANFirmware4355.Hashstore 1
>BCMWLANFirmware4364.Hashstore 1
>BCMWLANFirmware4377.Hashstore 1
>!ABCMWLANBusInterfacePCIe 1
|!ABCM5701Ethernet 10.3.5
@filesystems.hfs.kext 522.100.5
@BootCache 40
@!AFSCompression.!AFSCompressionTypeDataless 1.0.0d1
@!AFSCompression.!AFSCompressionTypeZlib 1.0.0
>!AVirtIO 1.0
@filesystems.apfs 1412.141.1
@private.KextAudit 1.0
>!AACPIButtons 6.1
>!ASMBIOS 2.1
>!AACPIEC 6.1
>!AAPIC 1.7
$!AImage4 1
@nke.applicationfirewall 303
$TMSafetyNet 8
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|EndpointSecurity 1
>!AXsanScheme 3
>!AHIDKeyboard 209
@kext.AMDRadeonX6200HWLibs 1.0
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>!AHS!BDriver 3430.1
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@kext.AMDRadeonX6000HWServices 3.1.0
|IOAVB!F 850.1
@!AGPUWrangler 5.2.6
@kext.AMDRadeonX6000Framebuffer 3.1.0
>!UAudio 323.4
|IONDRVSupport 576.1
>X86PlatformPlugin 1.0.0
>!AGraphicsControl 5.2.6
|IOAccelerator!F2 438.7.3
>IOPlatformPlugin!F 6.0.0d8
>!ASMBusPCI 1.0.14d1
|IO!BHost!CUARTTransport 7.0.6f7
|IO!BHost!CTransport 7.0.6f7
>!A!ILpssUARTv1 3.0.60
>!A!ILpssUARTCommon 3.0.60
>!AOnboardSerial 1.0
@kext.AMDSupport 3.1.0
@!AGraphicsDeviceControl 5.2.6
|IOSlowAdaptiveClocking!F 1.0.0
>!ASMBus!C 1.0.18d1
|IOGraphics!F 576.1
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>usb.networking 5.0.0
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>!AThunderboltDPInAdapter 6.2.6
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>!A!ILpssDmac 3.0.60
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@filesystems.hfs.encodings.kext 1
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@kec.pthread 1
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[warp9]

This crashing problem with 3rd party memory is becoming more and more common and is worrying. I wonder if Apple made a change to the memory controller and failed to inform memory suppliers. What's worse is OWC keeps cropping up-- normally a bastion of "it just works" memory for mac systems. Perhaps OWC is to blame.

I would contact OWC and send the crash log to them.

 

[0279317]

Did you try putting the original memory back to see what happens?

 

[jshcy]

Yes, thank you, I considered doing that. The iMac typically crashes once or twice a week. It's rather random (can't replicate the sequence of actions leading to it). I might have to wait for days before that happens and I would hate to sacrifice any performance gains with the 64GB of memory by re-installing the 8GB memory. Of course, I understand the risks associated with the random crashes too. It's just something that has never happened to me in the previous iMacs that I've owned over the years. By the way, I sent OWC a message with the crash report, but I have not yet heard back from them.

 

[wilberforce]

This seems to be another case of 2020 iMac crashing when using 4 sticks of OWC RAM

2020 iMac constant crash with 128gb RAM

The common denominator to everyone in this thread with issues, is 4 modules of OWC memory. This really looks like a manufacturing defect or oversight on the part of OWC.

forums.macrumors.com

 

[John90976]

I experience crashes 1-2 times a week but while I'm in a bootcamped Windows 10 partition of the SSD. It crashes into the macos bootscreen, often with the same audio from Windows clipping and just playing on repeat once booted into macos, taking yet another reboot to clear the audio. I've had my suspicions about the T2 but I also have four 8GB OWC RAM sticks installed. Maybe I'm not in macos enough to see it there as I like my red dead 2 on this 5K display, but crashing into macos from windows was a bit of a mindbending experience the first instant it happened. I would love to know what the heck is going on.

 

[jshcy]

Update: OWC sent out replacement memory modules and they have been fine (no issues) for over a week now. OWC customer service has been very responsive. Obviously, the original OWC modules were defective. So, if you have similar issues, get that memory replaced.