As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE ENROUTE OAK-VIS FLIGHT 8712 G600 LOST ALL INFO AND INDICATED AN AIR DATA COMPUTER FAILURE. THE PILOT ATTEMPTED TO TROUBLESHOOT THE PROBLEM BY TURNING IT OFF AND BACK ON AFTER A FEW MINUTES. THE FLIGHT WAS OPERATING IN AND OUT OF IMC, DECLARED AN EMERGENCY AND DIVERTED TO FAT. MAINTENANCE COULD NOT DUPLICATE ISSUE ON GROUND. REPLACED GDU620 WITH EXCHANGED UNIT. UPDATED SW AND CHECKED ALL CONFIGURATION SETTINGS. MAINTENANCE OPERATIONAL CHECK FLIGHT WAS SATASFACTORY.