Variable frequency clock control for microprocessor-based computer systems

• US 6,311,287 B1
• Filed: 10/11/1994
• Issued: 10/30/2001
• Est. Priority Date: 10/11/1994
• Status: Expired due to Term

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Compaq Computer Corporation (HP Inc.)
• Inventors: Schumann, Reinhard, Klumpp, Jim, Dischler, Richard J.
• Primary Examiner(s): BUTLER, DENNIS
• Application Number:
  US08/321,334
• Time in Patent Office: 2,576 Days
• Field of Search: 395/550, 395/750, 364/550, 364/557, 713/330, 713/320, 713/322, 713/323, 713/601
• US Class Current: 713/601
• CPC Class Codes: G06F 1/206 comprising thermal management
• CPC Class Codes: G06F 1/3203 Power management, i.e. event-based initiation of a power-saving mode
• CPC Class Codes: G06F 1/324 by lowering clock frequency
• CPC Class Codes: G06F 1/3296 by lowering the supply or operating voltage
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A computer system including a microprocessor and a circuit to provide a clock signal for the microprocessor is described. The circuit is responsive to a control signal for selecting a minimum clock signal frequency value and a maximum clock signal frequency value, with the maximum clock signal frequency value being adjusted in accordance with operating conditions of the central processor. Also the system includes a circuit which varies a magnitude of a supply voltage fed to the microprocessor in accordance with the temperature of the microprocessor and the operating frequency of the microprocessor. This arrangement provides an advantage to save power in computers. It is particularly advantageous for portable computers such as notebook computers to conserve battery charge, minimize heat dissipation in the microprocessor, and to minimize the size and weight of the battery used in the notebook for a given operating duration requirement.

Claims

1. A computer system comprising:

microprocessor;

means for generating a clock signal, said means including means responsive to a control signal for selecting a minimum clock signal frequency value and a maximum clock signal frequency value;

a microcontroller coupled to a system bus interconnecting said microprocessor to the computer system, wherein said microcontroller comprises;

means responsive to a signal indicating a temperature of operation of the microprocessor for adjusting the frequency of operation of the microprocessor in accordance with a present temperature of the microprocessor.

2. The apparatus as recited in claim 1 wherein further comprising:

means for sensing the temperature of operation of the microprosessor at a plurality of times; and

means for calculating an expected temperature based on temperatures sensed at said plurality of times.

3. The apparatus as recited in claim 2 wherein said means for sensing the temperature of the microprocessor comprises a thermistor.

4. The apparatus as recited in claim 2 wherein said means for generating a clock signal further comprises means for selecting the minimum value of clock frequency and said means for selecting a minimum and a maximum value of clock frequency comprises:

a storage register for storing a minimum value and maximum value of a clock signal; and

means responsive to a control signal provided from said means for adjusting including means for selecting the minimum value of the clock signal when the microprocessor is determined to be in an idle state and for selecting a maximum value of the clock signal when the microprocesser is determined to be in an active state, wherein said means responsive to a control signal further adjusts the frequency in accordance with a predicted temperature of said microprocessor, with said predicted temperature being determined in accordance with the present temperature and a change in the present temperature over at least one measurement time interval.

5. The apparatus as recited in claim 1 wherein said means for adjusting the frequency adjusts the frequency in accordance with a predicted temperature of the microprocessor, with said predicted temperature being determined in accordance with the present temperature and change in the present temperature over at least one measurement time interval.

6. The apparatus is recited in claim 1 wherein said means for generating a clock signal comprises:

a programmable phased lock loop which is fed digital data corresponding to either the minimum or maximum clock frequency.

7. The apparatus as recited in claim 5 wherein said apparatus further comprises:

means for varying a magnitude of a supply voltage fed to the microprocessor in accordance with the temperature of the microprocessor and the operating frequency of the microprocessor.

8. The apparatus as recited in claim 7 wherein said means for varying a magnitude of a supply voltage comprises:

a DC to DC converter to provide a supply voltage to the microprocessor; and

a switchable voltage divider, responsive to a control signal for varying a voltage across the voltage divider in accordance with the state of the control signal, with said voltage across the voltage divider being fed back to the DC to DC converter to change the magnitude of the supply voltage from the DC to DC converter.

9. A computer system comprising:

a microprocessor;

means for varying a magnitude of a supply voltage fed to the microprocessor in accordance with the temperature of the microprocessor and the operating frequency of the microprocessor including;

a DC-to-DC converter to provide a supply voltage to the microprocessor; and

a switchable voltage divider, responsive to a control signal for varying a voltage across the voltage divider in accordance with the state of the control signal, with said voltage across the voltage divider being fed back to the DC-to-DC converter to change the magnitude of the supply voltage from the DC-to-DC converter.

10. The computer system of claim 9 further comprising:

means for generating a clock signal, said means including means responsive to a control signal for selecting the minimum clock frequency value when the microprosessor is in an idle state;

means for selecting the maximum clock frequency value when the microprocessor is in an operating state; and

means for adjusting the maximum clock frequency value in accordance with operating conditions of the central processor.