Оригинальный сообщение: Dan ,
I would start with the basics here: Have you checked your systems firmware? Here's the Apple T/N to follow: [https://support.apple.com/en-us/HT201518|About EFI and SMC firmware updates for Intel-based Mac computers]. How full is your SSD? You should leave about 1/4 to 1/3 of free space, more if you have a smaller SSD. How much RAM do you have? Yosemite needs at least 4GB of RAM, I like my systems with 8GB.