All Posts by Date or last 15, 30, 90 or 180 days.
also by Lloyd: diglloyd.com photography and WindInMyFace.com

Thank you for buying via links and ads on this site,
which earn me advertising fees or commissions.
As an Amazon Associate I earn from qualifying purchases.

Other World Computing...
B&H Photo...
Amazon
As an Amazon Associate I earn from qualifying purchases.
Upgrade the memory of your 2020 iMac up to 128GB
Upgrade the memory of your 2020 iMac up to 128GB

Apple Kernel Bug? 2015 iMac 5K Runs at 0.8 GHz When Cold, Even with Warm Air Out Rear Vents

Mac wish listall 15" Apple MacBook Pro 2017 modelsMPG gets credit if you buy through those links.
MPG tested a fully-loaded 2017 MacBook Pro with 1TB SSD.
Suggested accessories include the OWC Thunderbolt 3 Dock, the 1TB Envoy Pro EX.

Back in August, I reported on the 2015 MacBook Pro dropping to 0.8 GHz when temperatures rose, making it unusable for any useful work.

It turns out that cold also causes an issue, and this time it looks like a bug that does not go away without shutting down and restarting—rebooting did not fix the problem.

Conditions: 33°F inside of my Mercedes Sprinter photography adventure van, rapidly warming interior to 73°F within about 20 minutes.

Clock speed starts at 0.8 GHz and stays there

The graph below from Intel Power Gadget shows the 2015 iMac 5K running like molasses in a refrigerator, at 0.8 GHz. All four CPU cores are at 100%, but at 0.8GHz. User tasks do run, but very slowly, in slow motion.

Initial ambient temperatures of 33°F might explain this behavior as some self-protective measure, but rebooting twice and with warm air coming out of the back of the iMac and with cabin temperature of 73°F the iMac still ran at 0.8 GHz with no sign of changing behavior.

Not until the iMac was shutdown and rebooted did it run at normal speeds.

The Intel CPU seems unlikely to be responsible, since it was at 33.3°C as shown below. Accordingly, a reasonable theory is yet another Apple macOS kernel bug.

Intel Power Gadget showing 2015 iMac 5K running at 0.8 GHz

When this behavior occurs, kernel task consumes all four real CPU cores.

With 2015 iMac 5K running at 0.8 GHz, kernel task consums all four real CPU core at 100%
View all handpicked deals...

Apple 16.2" MacBook Pro with M1 Max Chip (Late 2021, Space Gray)
$4899 $3999
SAVE $900

diglloyd.com | Terms of Use | PRIVACY POLICY
Contact | About Lloyd Chambers | Consulting | Photo Tours
Mailing Lists | RSS Feeds | Twitter
Copyright © 2020 diglloyd Inc, all rights reserved.
Display info: __RETINA_INFO_STATUS__