A power supply for a computer system manager, wherein the power supply has its own secondary power source operable when input power to the system manager no longer meets preset threshold values. The power supply functions in one of a discrete number of power modes depending upon the amount of energy available from either the computer input power or the secondary power source. The power supply switches to one of the group of power modes to conserve secondary power when the computer input power is no longer available. The power modes are controlled by a power mode controller which selectively directs power to discrete components of the system manager as a power conservation technique. The power mode controller always energizes the random access memory of the system manager in order to maintain data integrity. Upon detecting insufficient energy within the secondary power source, the power mode controller terminates all power flow from the power supply, including power flow to the random access memory, at which point the entire system has lost all data and configuration settings.