My Early 2011 MacBook Pro has been having some video issues. Bad ones. Black bars, fuzzy and shaking images, crazy resolutions. These are all the signs of a failing video card. But the symptoms didn't happen all the time, the machine would be solid one moment and then bonkers then next.
What is happening is the sign of a feature in action: automatic graphics switching between video subsystems. Most MacBook Pros since 2010 sport two GPUs: the integrated Intel video and the discrete GPU. The switching technology examines the framework of the application being called upon and whether its performance will be improved by using the higher-performing GPU, then the system will switch to the better one for the document, app and content task at hand.
Of course, this can mean a strain on battery life: The more-powerful GPU consumes more power. Apple admits this in a Support Note, since the switch may not reverse itself if the graphics programs are kept open.
On Mac computers that support automatic graphics switching between two graphics processors, some software using OpenGL technology may engage the discrete, higher performance graphics automatically. For best battery performance, consider quitting OpenGL-based applications when you finish using them.
However, an Ars Technica article about improving battery performance on Retina MacBook Pros, warns that many applications may call upon the better GPU. Some are not so obvious, even to the knowledgeable user.
But running the discrete GPU also consumes considerably more power. And seemingly innocuous apps, including Twitter, Reeder, Transmit, PathFinder, Skype, Delicious Library, Drive Genius, and NetNewsWire, among others, could cause the discrete GPU to power on and run as long as they are open. So instead of 7 hours of continuous operation, the Retina MacBook Pro running any of these apps might instead only last 6 to 6.5 hours under similar conditions.
Enter Cody Krieger and his gfxCardStatus application. It pops a Menu Bar icon that displays the status of the GPU being used: "I" for the integrated GPU and "D" for the discrete GPU. It's useful information.
But how does this help me with my MacBook Pro's problematic discrete GPU? After I mentioned my situation at the recent BMUGWest user group meeting, http://bmugwest.com moderator Lorca Hanns pointed out that there was another side to gfxCardStatus — it lets users force the more battery-friendly graphics GPU and disallows automatic switching. This lets me avoid the problem GPU altogether. This setting can only be invoked when there aren't any discrete GPU-dependent apps running.
I note a potential automatic graphics switching bug reported on Will Wiriawan's Portfoliography blog. It appears to affect the color lookup table.
There seems to be a little bug that affects a small number of MacBook Pro (with dual graphic card) machines; the display would turn blueish when the discreet graphic is in use by way of the Automatic Graphic Switching.
Wiriawan points to a fix. However, it also may be fixed with Krieger's little app.