OS 10.6.8 late 2009 imac. Yesterday and twice this morning, after booting up, the desktop screen went black for a few seconds and then the desktop became normal. I have just rebooted and it never reoccurred. Is this an indication of something I should know about? Secondly, for the first time I could hear the fan blowing upon boot-up so I rebooted and again the fan was very audible but after about 2 minutes, it was inaudible as usual. I realize the fan is is for cooling purposes but it must run at a very slow speed for me not to know it is actually running. Am I reading too much into this? jaybass
OS 10.12.6 iMac (Retina 5K, 27", 2017, 3.4 GHz Intel Core i5, 24 GB RAM, 2400 MHz DDR4. Sierra. 10.12.6 SuperDuper. 1 TB Lacie HD, Noise Ninja.