My laptop (mid-2012) won't boot past the Apple logo. Safe boot won't work either.
Disk utility in recovery mode and fsck in single-user mode both say the hard disk is fine. Verbose mode report has several lines of
disk1s1 I/O error, however.
This machine apparently does not have the diagnostic tools on it, as booting while holding down the 'D' key takes me to Internet recovery. I tried that to see if the online diagnostics would run but it gets stuck on the spinning globe screen after I enter my wifi password.
I'm thinking this could be the hard disk, the hard disk cable, or the main board. How do I tell for sure so I don't spend money unnecessarily?