For FCPX (and many other apps) under the new Apple OS X Mavericks, apps will by default, attempt to save processing for foreground apps by doing something new called “App Nap” – and that will cause background rendering to STOP unless you turn it off.
This is all news to me so I thought I'd share!
APP NAP Strikes!
This morning I saw this on twitter…
— John Flanagan II (@oflanada) October 25, 2013
From MacWorld – more on App Nap
What makes the Mac ideal for getting work done is that you can have multiple Mac apps open at the same time, all of them chugging away at the tasks you need to finish. The drawback is that an app that’s open in the background may seem as if it’s doing nothing when it’s actually drawing on your Mac’s hardware resources. If you’re working on a Mac laptop, that activity can take a toll on its battery life.
You could quit the background apps, but that isn’t always practical. As an alternative, Apple developed App Nap, a feature that works behind the scenes to better manage the work that open apps are doing. Essentially, App Nap senses when an app isn’t doing anything and puts that app into a low-power state. This state involves timer throttling, which reduces an app’s need to use the CPU; I/O throttling, which gives the app low priority for accessing storage or a network connection; and priority reduction, which assigns an app a smaller portion of a CPU’s processing time. Apple says App Nap can reduce the amount of power that apps are using by as much as 23 percent.
How does App Nap work? It looks for apps that fit a specific set of criteria. The app’s windows have to be hidden, either in the Dock or behind other windows, and it can’t be playing music or other audio. App Nap also checks to see if the app has specifically disabled App Nap and makes sure it doesn’t implement any power-management features of its own. If an app meets all of these requirements, App Nap goes to work. When you need to use one of these background apps, App Nap deactivates, and the app switches to full speed.
If an app is playing audio, downloading a file from a server or the Internet, or doing something else in the background that requires the full attention of your Mac’s resources, App Nap will not activate. Also, software developers can write their apps so as to disable App Nap.
Users have the ability to disable App Nap in Mavericks for a particular app. To do so, open a Get Info window for the app (click the app and press Command-I, or click the app and select File > Get Info), and you’ll see a checkbox labeled Prevent App Nap. Click that checkbox.
(cover photo credit: snap from the MacWorld story)