Macbook Air CPU throttled, flatlined at .80 GHz???
I have a MacBook Air, 13" 2012 A1466, with an i7 2GHz processor, 8GB ram. The logic board was recently replaced and the new board is remarkably slower. After browsing this site I came across Intel Power Gadget, installed and ran it. The frequency lines do not move, and it lists .80GHz as the IA (speed). Temperatures are a constant between 58-60 even with no activity. Fan speed is at 2000 and doesn't go up or down regardless of use. I have no errors when running diagnostics.
Geekbench 3 scores are unreasonably low, I get between 650/700 on average.
I troubleshooted and searched for answers. I tried resetting the SMC, the NVRAM, then restoring from a Time Machine backup, then tried a fresh install, and finally swapped out the SSD for another just in case that was the problem.
OS X is up to date, EFI and SMC are up to date, battery is brand new (and I tried 2 others). Tried disconnecting everything internal, the keyboard, touchpad, Airport card, LCD cable, reseated everything, booting one at a time just in case something was broken.
I have absolutely no idea what would cause the CPU to be locked at 800MHz. It seems to be some sort of protective mode? I've seen a few other people with this problem on here, but none with a solution.
Can anyone help? I'm looking for the Apple person equivalent to the "Click and Clack, the Tappet Brothers"!
MacBook Air (13-inch Mid 2012), OS X El Capitan (10.11.6)