Video subsystem power management apparatus and method
First Claim
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1. A method of reducing power consumption in a computer system, comprising the steps of:
- generating signals to a display of the computer system to reduce power to the display;
reducing power consumption in a video subsystem of the computer system, comprising the steps of;
inactivating a pixel clock which drives a RAMDAC, thereby reducing power consumed by the RAMDAC; and
decreasing the frequency of a memory clock for driving a video controller by a predetermined factor, thereby reducing the power consumed by the video controller.
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Abstract
Power is conserved in a video subsystem by inactivating a pixel clock (PCLK) and reducing frequency of a memory clock (MCLK) responsive to an indication of user inactivity. The inactivation of PCLK reduces the power consumed in the RAMDAC, frame buffer, phase lock loop (PLL) clock circuit, and to a smaller extent, the video controller. Reducing the frequency of MCLK conserves power in the video controller and the PLL, while maintaining the integrity of the data in the frame buffer. Significant power savings can be accomplished with minimal BIOS or video controller programming and minimal transfer of state information prior to power-down.
79 Citations
21 Claims
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1. A method of reducing power consumption in a computer system, comprising the steps of:
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generating signals to a display of the computer system to reduce power to the display; reducing power consumption in a video subsystem of the computer system, comprising the steps of; inactivating a pixel clock which drives a RAMDAC, thereby reducing power consumed by the RAMDAC; and decreasing the frequency of a memory clock for driving a video controller by a predetermined factor, thereby reducing the power consumed by the video controller. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A computer system for minimizing power consumption in a video subsystem comprising:
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a CPU connected to a system bus; a plurality of peripherals connected to said CPU by the system bus; a monitor; and a video subsystem connected to said monitor and connected to said CPU by the system bus, comprising; clock circuitry for programmably generating a first clock and a second clock, such that said first clock can be disabled responsive to a first control signal and said second clock can be reduced in frequency responsive to a second control signal; a frame buffer memory; a RAMDAC driven by said first clock coupled to said frame buffer, the power consumed by said RAMDAC dependent upon the frequency of said first clock; a video controller driven by said second clock and coupled to said frame buffer, said video controller controlling memory cycles in said frame buffer responsive to said second clock; and circuitry for inactivating said first clock and reducing the frequency of said second clock responsive to an indication of inactivity to reduce power consumption in said clock circuitry, said frame buffer and said RAMDAC. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A method of managing power consumption in a computer system, comprising:
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monitoring a computer system for activity; performing power management in a video subsystem of the computer system in response detecting inactivity in the computer system, comprising the steps of; increasing the rate at which a video controller refreshes memory in a frame buffer by a predetermined factor; and decreasing the frequency of a memory clock for driving the video controller by the predetermined factor, thereby reducing the power consumed by the video controller and reducing the frequency of memory cycles to a frame buffer, while maintaining a normal refresh rate. - View Dependent Claims (17, 18, 19, 20, 21)
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Specification