Battery operated computer power management system

In a battery operated computer having a main processor for executing application programs under the control of an operating system;

• a plurality of I/O devices;
• and a dynamic random access memory (DRAM) for storing said application programs and said operating system for execution by said main processor;
• the combination comprising:
• a power distribution system including a power control register operable under the control of said main processor for controlling power distribution in said computer, said power distribution system being connectable to a replaceable main battery for powering said computer to operate said main processor, said I/O devices, and said DRAM, said power distribution system being further connectable to a standby battery for powering said DRAM when said main battery is removed;
• said power control register being connected to different lines of said power distribution system and having different bits that are selectively set by said main processor to provide on/off control of power distributed along said lines;
• first monitoring means including a power management processor (PMP) connected to said power distribution system for monitoring predetermined conditions including power level of said main battery and generating interrupt requests upon the occurrence of predetermined first conditions, said monitoring means being operative to generate a suspend interrupt request immediately prior to said main battery becoming fully discharged;
• interrupt means connected to said first monitoring means and including an interrupt controller for transmitting an interrupt request signal to said main processor in response to said suspend interrupt request from said first monitoring means;
• storage means connected to said main processor for storing a plurality of interrupt handlers including a suspend interrupt handler;
• a clock speed controller selectively settable to operate said main processor at one of a plurality of predetermined rates;
• a user actuated first switch for selecting one of said predetermined rates;
• a non-volatile storage for storing a user selectable energy option for accomplishing either a high performance objective or a long battery life objective;
• a user actuated second switch selectively settable to a "manual" position and to an "automatic" position;
• speed control means connected to said clock speed controller, said speed control means being operative when said second switch is in said "manual" position to set said clock speed controller to operate at the rate selected by said first switch, said speed control means being further operative when said second switch is in said "automatic" position to set said clock speed controller in accordance with said energy option and operate said processor at a high rate when said high performance objective is selected and operate said processor when said long battery life objective is selected by switching between a high rate and a low rate dependent on system activity;
• said main processor being operative in response to said interrupt requests from said interrupt means to selectively execute said interrupt handlers and set said power control register in accordance therewith to thereby control power distribution in said computer, said main processor being operative to execute said suspend handler immediately prior to said main battery becoming fully discharged to first store CPU information from said main processor in said DRAM and then power down said computer whereby said standby battery retains information in said DRAM when said main battery is removed for replacement;
• and restoration means responsive to connecting said power distribution system to a source of power, after said main battery has been removed, to power up said computer, restore said CPU information from said DRAM into said main processor, and resume normal operation of said computer.