nearly every technician I've spoken to will have you restore defaults and clear the NVRAM before doing a reinstall.  this would set the CPU speed to normal  and not to compatible as i would suspect you found your system in.

Sadly or luckily, I am not a computer technichian. I am a user and I expect consumer electronics to be managable without  a training program from every company. I did select the restore config as a first step. As I said there were no manuals and the documentation on the site was a bit skimpy.

 

Thanks for reading.