On March 1, 2010 (UTC), many of the original "fat" PlayStation 3 models worldwide were experiencing errors related to their internal system clock. The error had many symptoms. Initially, the main problem seemed to be the inability to connect to the PlayStation Network. However, the root cause of the problem was unrelated to the PlayStation Network, since even users who had never been online also had problems playing installed offline games (which queried the system timer as part of startup) and using system themes. At the same time many users noted that the console's clock had gone back to December 31, 1999. The event was nicknamed the ApocalyPS3, a play on the word apocalypse and PS3, the abbreviation for the PlayStation 3 console.

What part of the original model PS3s starting causing problems in March of 2010?