Code 8 is a problem with the CPU.
Unplug the power cable from the back of the power supply.
Remove the battery from the board for 10 minutes and then put it back in.
Remove all hardware but CPU, GPU, and one RAM stick.
Plug the power cable back in.
Cross your fingers, toes, and eyes.
Power the computer up.
Go into the BIOS and put the settings back to what they were then save.
Shut down and reinstall the rest of the system.