To restart the PSU BIST, what must be done?

To restart the Power Supply Unit (PSU) Built-In Self-Test (BIST), disconnecting the AC power cord for 15 seconds is the correct action. This process allows the internal components of the PSU to reset and clear any error states that may exist from previous operations. By unplugging the power cord, you effectively cut off all power, thereby allowing the PSU to reset its internal diagnostics and prepare for a fresh start when the power is restored.

The BIST is a diagnostic feature in certain power supplies that checks for proper operation upon power-up. When the power supply is disconnected for a short period, any latching conditions or errors are cleared, enabling the system to begin a new diagnostic cycle when power is reintroduced. This method is both straightforward and effective, making it the preferred approach for restarting the PSU BIST.

Other methods, such as pressing a reset button or turning off a power supply switch, might not provide the full reset needed for the PSU diagnostic systems. Additionally, removing the PSU from the PC case can be unnecessary and cumbersome unless there is a physical issue that needs to be addressed.