Stalling for detach from IntelAccelerator

My iMac recently started to become intermittently unresponsive while running OS X El Capitan 10.11.6 (I know, I’ll update to Sierra soon enough). I would be going along fine and then everything grinds to a halt for some amount of seconds before anything I had tried to do in the interim sped along. Watching Activity Monitor was wild, it would also freeze and then speed through 20 seconds worth of updates in a second or two.

Some message board posting suggested that virtualization platforms like VirtualBox could be doing it with a bug in 3D acceleration support, but I wasn’t running any at the time. I stopped Little Snitch, my only non-Apple kernel extension and still had the hang ups. Using Console.app I found messages warning of “Stalling for detach from IntelAccelerator” and “Stalling for detach from nvAccelerator” that happened before the momentary freezes along with a lot of udpates from WindowServer about problems drawing windows. That had me worried it might be the video card or something else hardware related.

It turns out it’s Apple’s fault and they had already pushed a software update to fix it. If you’re having any freezing or hangup issues make sure you have installed Security Update 2016-003 Supplemental (10.11.6). No hangups yet, fingers crossed!