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So I bought a mid 2012 MacBook Pro, low price so I went for it. It was super super slow the slowest thing I’ve ever used. The mouse would lag around when you moved it. Safari would take minutes to just open. Any app was just unusable. So I did some research and it seemed like I needed to upgrade to an SSD and more RAM. I’m new to MacBooks so that’s just what I thought I should do since everybody who has done the upgrade says there’s a night and day difference. So I bought a 500 GB SSD and 16 GB of RAM and still no change. I can’t even watch a YouTube video without it jumping every 2 seconds. I’m not sure if it’s the way I copied the OS to the SSD so tell me if I did something wrong . I shutdown the system plugged in the SSD with a USB adapter and turned it on while holding command and R as I was told by YouTube. Then I went to “reinstall OS X” then I just clicked my SSD and let it download High Sierra. And yes, I did erase the SSD in disk Utility before I downloaded it. Again, I’m super new to upgrades and macs so I’d appreciate any help I can get to make my Mac usable and smooth thank you.
Examine the logic board right at the crimped end of the heat sink. You are looking for a oily type stain. If you see it, the heat sink has leaked, you are overheating and throttling down. Replace it: MacBook Pro 13" Unibody (Mid 2012) Heat Sink MacBook Pro 13" Unibody Mid 2012 Heat Sink Replacement
Are the fans noisy? The cursor lag can be caused by a bad battery, liquid damage on the board causing the SMC or the temperature sensors connected to the SMC to be not functioning correctly.
