Secondary cache system for portable computer

A power management system for a portable computer, wherein the portable computer includes a microprocessor with a central processor and an internal cache memory, the power management system comprising:

• a secondary cache memory in said portable computer that is electrically connected to said processor for reducing the number of wait states encountered by the central processor;
• control logic electrically connected to said central processing unit and to said secondary cache memory,
• wherein said control logic monitors the activity of said central processor and turns off said secondary cache memory when the processor is inactive,
• and wherein the control logic turns on the secondary cache memory when the number of wait states become excessive.

A system for conserving power in a portable computer, said portable computer including a processor and conventional memory, the system comprising:

• a cache for expediting the transfer of data between the processor and the conventional memory, said cache including:
• a cache controller with a control register that includes a first bit, a second bit and a third bit, each of said bits having two states;
• and
• a cache memory comprised of SRAM circuits with a cache directory for storing addresses and a memory buffer with lines for storing data;
• a control and power management logic connected to said cache controller, wherein said control and power management logic:
• changes the state of the first bit to control power to the cache memory;
• checks the state of the second bit to determine if lines in the cache memory must be flushed to conventional memory prior to turning off power to the cache;
• and
• checks the state of the third bit to determine if data in said cache memory is valid after said cache is turned on.

A method for conserving power in a portable computer that includes a processor, a system memory and a secondary cache memory, comprising the steps of:

• (a) turning on the secondary cache memory while maintaining the processor in an operational state;
• (b) determining if the processor is inactive;
• (c) turning off the secondary cache memory if the processor is inactive;
• and
• (d) determining if the processor is active.

A method for conserving power in a portable computer that includes a processor, a system memory and a cache memory, comprising the steps of:

• (a) turning on the cache memory by changing the state of a control bit;
• (b) determining if the processor is inactive;
• (c) turning off the cache memory by changing the state of the control bit if the processor is inactive;
• and
• (d) determining if the processor is active.