I've been having an intermittent problem with my late 2013 27" iMac for more than a year now and it seems to be getting more frequent.
Basically, I could be doing anything on my iMac (or nothing at all!) and I suddenly hear the fans spin up to what sounds like max speed. When the fans spin up like this, the applications I am using (typically Chrome, but others too), will work for a little while, ~30 seconds, and then become unresponsive. I am not even able to restart the iMac from the Apple menu (it just doesn't respond). Eventually, I get the "rainbow circle" (beach ball?) mouse cursor and I can't do anything else other than move the mouse around. If I keep waiting, the screen goes black and if I wait a longer time the black screen gets a circle with a slash through it. What I normally do is just power cycle the iMac as soon as I hear the fans spin up and the applications become unresponsive. The system crashes this way usually at least once and often a few times per day if I use it a lot.
Here's what I've done so far to troubleshoot:
After power-cycling, I go into Console.App, and select "Crash Reports" on the sidebar, it is always empty. Is it correct to assume that this means it was not an application that crashed?
I've tried sifting through the logs looking near the time of the crash, and I don't notice anything obviously strange, basically just normal looking logs and then boot-up messages. The problem is there's A LOT of messages. I am looking for "grave" sounding messages, but I honestly don't know what, exactly, to look for. Is it possible there's no clues in the logs?
I've run Memtest86, it passes all four passes. No failures detected.
I've wiped the machine and re-installed the OS about 3 times. The problem persists. I am on Catalina now, but this has been happening even with the previous OS, Mojave.
I've tried not using some Applications that are long-running. I've tried switching from Chrome to firefox, and disabled dropbox. No change.
Fan RPM's and Die Temps appear normal. I do notice that when the system crashes, these no longer update. Could it be a thermal issue that happens so fast, the system crashes before the sensors log the problem? I am not doing anything super-taxing to the system. I have noticed at least one spike in CPU temperature before around the time of a crash, but I haven't been able to see that consistently.
I cleared out the
/Library/Logs/DiagnosticReportsdirectory, and used the machine normally until the next crash. After the crash, the directory had a bunch of files. None of them had a suspicious filename extension (eg .panic, .spin, .tailspin). Only one had a timestamp that was at at most a few minutes from when the crash happened: "
Google Chrome Helper (Renderer)_2021-02-02-082350_MY-MACHINENAME.wakeups_resource.diag". Sadly, I don't have even the foggiest idea what this log file is trying to tell me. The central issue seems to be something about "wake-ups", here's part of it (I can upload the whole thing somewhere if someone thinks this has critical clues):
Date/Time: 2021-02-02 08:21:48 -0500 End time: 2021-02-02 08:23:50 -0500 OS Version: Mac OS X 10.15.7 (Build 19H114) Architecture: x86_64h Report Version: 29 Incident Identifier: 52354DFF-B2C8-497A-8421-369191E5D935 Data Source: Microstackshots Shared Cache: 0x7b5a000 57CFFC05-B33E-3B2A-9BBC-D3A0F410A70D Command: Google Chrome Helper (Renderer) Path: /Applications/Google Chrome.app/Contents/Frameworks/Google Chrome Framework.framework/Versions/88.0.4324.96/Helpers/Google Chrome Helper (Renderer).app/Contents/MacOS/Google Chrome Helper (Renderer) Identifier: com.google.Chrome.helper.renderer Version: 88.0.4324.96 (4324.96) PID: 18226 Event: wakeups Action taken: none Wakeups: 45001 wakeups over the last 122 seconds (370 wakeups per second average), exceeding limit of 150 wakeups per second over 300 seconds Wakeups limit: 45000 Limit duration: 300s Wakeups caused: 45001 Wakeups duration: 122s Duration: 121.77s Duration Sampled: 87.46s Steps: 21 Hardware model: iMac14,2 Active cpus: 8 Fan speed: 1202 rpm
Disk Utility "first aid" passes with exit code 0, disk appears to OK.
3rd Party kernel extensions. Using kextstat and grepping for kernel extensions,, I get the following. Basically just virtualBOX and Dropbox. I know the crashes still happen even when these aren't running. In today's crash, virtual box was not open, and not running a VM. Dropbox was on but not syncing anything.
admin@mt-iMac DiagnosticReports % kextstat | grep -v com.apple Index Refs Address Size Wired Name (Version) UUID <Linked Against> 160 3 0xffffff7f84180000 0xf2000 0xf2000 org.virtualbox.kext.VBoxDrv (6.1.18) 9C1C33DF-8061-30A2-9266-C9284816A6A2 <8 6 5 3 1> 163 0 0xffffff7f84272000 0x8000 0x8000 org.virtualbox.kext.VBoxUSB (6.1.18) 51E577B4-43B6-359F-B817-9C63A69E7943 <162 160 59 8 6 5 3 1> 164 0 0xffffff7f8427a000 0x5000 0x5000 org.virtualbox.kext.VBoxNetFlt (6.1.18) 96E530DE-E34D-3447-89A5-FCF6646AE47E <160 8 6 5 3 1> 165 0 0xffffff7f8427f000 0x6000 0x6000 org.virtualbox.kext.VBoxNetAdp (6.1.18) 63EFABA5-3341-3BEB-B47A-AAFCDD7312A5 <160 6 5 1> 173 0 0xffffff7f80fb6000 0x6000 0x6000 com.getdropbox.dropbox.kext (1.13.0) 4FFF485B-204E-3E48-BC54-C1D406AB9E75 <8 6 5 2 1> admin@my-iMac DiagnosticReports %
No third party hardware was connected, just Apple keyboard + trackpad.
I will try running safemode for some days and see if these crashes still occur. I understand that will mean it's a hardware issue, but what component/sub-system?
Switching to safari as my browser has kept the machine stable for 3 days and counting. Still curious about the root cause.
What else can I try? I am comfortable with disassembly and swapping parts, and in fact, am thinking about an upgrade from fusion drive to ssd and increasing the RAM, but if the system is unstable, I am hesitant to spend the bucks on an upgrade unless I can also find/fix the root cause of these crashes.
Any other ideas?
Here's the system...
Model Name: iMac Model Identifier: iMac14,2 Processor Name: Quad-Core Intel Core i7 Processor Speed: 3.5 GHz Number of Processors: 1 Total Number of Cores: 4 L2 Cache (per Core): 256 KB L3 Cache: 8 MB Hyper-Threading Technology: Enabled Memory: 16 GB Boot ROM Version: 4220.127.116.11.0 SMC Version (system): 2.15f7