Tandem Computers Incorporated

Garry Easop

Murali Basavaiah

Robert L Jardine

Larry D Reeves

An apparatus and method for tolerating failure of the AC power source in a power supply switchable between the AC power source and a battery, in a processor system having a set of one or more components subject to being powered down. When the failure of the AC power source is recognized, the power supply is switched from the AC power source to the battery. For a first period of time, the battery powers the processor system with all components powered on. The battery then powers the processor system with the specific set of components powered off for a second period of time. In one embodiment, a determination is made that the battery can power the processor system with the set of components powered down for a predetermined period of time. A determination of the first period of time is then made as the capacity of the battery exceeding the predetermined period of time, if the excess capacity is used to power the processor system with the set of components powered on. In effect, a processor system incorporating one embodiment of the invention rides through a first period of a power outage, operating as normal and masking the loss of AC power. For a second, predetermined period, the processor system shuts down optional hardware and maintains the state of memory using the battery power.

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Sunnyvale, CA, United States of America

Garry Easop