![\"Allister's](\"https:\/\/podfeet.com\/NosillaCast\/NC_2014\/NC_2014_06_01\/allister_imac_screen.png\")
<\/p>\nGreetings fellow NosillaCastaways. Allister here from New Zealand again with a tale of trouble. First, the problem to be solved. How about being called out in the live chat room last week to provide some content? No? OK, how about you\u2019ve taken two weeks off work to get in some quality time with XCode and not even half way into the first week your Mac decides to freeze? Often. Yeah, THAT\u2019S a problem to be solved.<\/p>\n
Fortunately I am now able to (mostly) trust my Mac enough to compose and record this. I\u2019m sure your Mac will run reliably until the end of its days, but if I\u2019m wrong about that, maybe this tale will help you out.
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\nI have been noticing some occasional odd behaviour from my Mac recently, such as failing to complete the shutdown process or failing to wake from sleep, but on each occasion a forced reboot brought everything back to normal and I carried on. A forced reboot is a last resort, so I always try to get a normal shutdown either by using the Apple menu if it\u2019s visible and operable or pressing Command-Option-Control-Eject. This may result in some Save windows so pressing Enter a few times afterwards can help. When that doesn\u2019t work, pressing and holding the power button for 5 seconds will always work. It\u2019s a last resort because it cuts power to your system instantly and if it was writing to disk at the time \u2013 well, all bets are off on whether all your data is safe.<\/p>\n
So this had happened to me a handful of times over a few months. Yesterday, I was reading a web page in Safari when my screen suddenly went black and I had to force power off the Mac. After powering back up I expected everything to be normal again. But it wasn\u2019t. The fun was really beginning to happen.<\/p>\n
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If you use desktop spaces on your Mac you may have noticed that as you slide between the spaces, there is a black bar between them. After the login screen \u2013 all normal \u2013 my desktop appeared. But it was partially scrolled across to the next space with that big black stripe about a quarter of the way in from the right of the physical screen. I wasn\u2019t touching anything! And the icons on the desktop and their text weren\u2019t looking right. They were all broken up into lines and flickering slightly. Gulp! I waited to see if this would right itself. Nope, it got worse. The screen went briefly black and then the desktop re-appeared. The view was now flipped left to right and had a whole lot of green bits flickering away madly over the entire desktop. I was reminded of those screensavers based on The Matrix movie. Clearly a forced reboot was required. Again.<\/p>\n
I decided updating my clone backup would be a good idea! I grabbed my clone backup drive, inserted it into my drive \u2018toaster\u2019 and launched Carbon Copy Cloner. The app\u2019s icon bounced in the dock but no window appeared. Yikes! This was not good. Another keyboard shortcut \u2013 Command-Option-Escape to bring up the Force Quit window. Carbon Copy Cloner (Not responding). iTunes (Not Responding). Safari (Not responding). Airmail (Not responding). And more. Oh dear! Time to shut down again. And this time, stop those apps from launching, as one of them could be the problem. I managed to begin a normal shutdown and unticked the \u201cReopen windows when logging back in\u201d checkbox. It still took a forced reboot to get it back again.<\/p>\n
Powered up again with no apps running, I launched Carbon Copy Cloner and started an update of my clone. To give it the greatest chance, I touched nothing else while it was running. An hour later it reported a successful clone, at which time I ejected and unplugged the drive. If any kind of corruption was possible, I did not want the clone to be reachable.<\/p>\n
Now I was backed up (phew!) so what was ailing this machine? It seemed to be fine for the moment, so I decided to look in my Console logs. The Console app is in the Applications\/Utility folder and allows you to look at the system logs which can tell you all sorts of interesting information. By default it displays all messages and this is a good start point for troubleshooting. I began scrolling back through time and noted the highlighted BOOT_TIME entries which each mark the beginning of a boot process. I first concentrated on what happened during that crazy graphics time and noted lots of GPU errors and debug output. Clearly something wasn\u2019t right on the graphics front, but what about that first issue? By using the search field, I was quickly able to pinpoint all my boot starts for the day and then looked immediately prior to the first one. Nothing. No GPU errors, nothing from Safari or anything else. Was this a graphics problem or not?<\/p>\n
![\"console](\"https:\/\/podfeet.com\/NosillaCast\/NC_2014\/NC_2014_06_01\/allister_console.png\")
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Some further rooting around in the logs brought up a few messages which implied that a screen had been unplugged. This is interesting because I have a MacBook Pro and no external monitor. The graphics were definitely taking centre stage. I followed up on some information in the NosillaCast Google+ community in response to a similar problem reported by Dorothy. The symptoms didn\u2019t seem like a good match, but I followed some of the recommended steps including an NVRAM reset and checking all my disks for errors. I also mentioned it to a friend online who asked \u201cIs it NVidia?\u201d It is. \u201cThey have a reputation for failing in Macs\u201d he said. Hmmm.<\/p>\n
I realised there was a simple test to see if the NVidia graphics card was the problem. I started a few simple apps \u2013 all remained fine \u2013 and then I started Photoshop. Its splash screen appeared and\u2026 my Mac was frozen solid. A forced reboot later, I employed another tool \u2013 Activity Monitor. Under Mavericks, in the Energy tab, it lists all the applications and shows whether they require the dedicated graphics card. Sure enough, with the system working, all said \u201cNo.\u201d<\/p>\n