Automatic power saving mode configuration

Publishing Venue

IBM

Abstract

A system for determining the state of a microprocessor, working or idle, is disclosed. Such system allows to modify the power supply and the clock speed so as to reduce the power consumption of the devices.

Automatic power saving mode configuration

As described on figure 1, a microprocessor has external RAM , ROM, and peripherals. When it is working normally, a lot of accesses can be seen from the microprocessor to those external devices , but when it is idle, the microprocessor accesses remain on the ROM in order to jump on it's current instructions. So, the idea of the invention is to count the number of external accesses to determine the state of the processor.

    Figure 2 illustrates the invention: the RAM, Perif1 and Perif2 accesses increment the counter , while the ROM accesses decrement it. When the value of the counter is more than a predetermined threshold e.g., 50, it's output decode is set to 1 and the clock rate is set to its maximum value, but when the counter value is less than 50, the idle mode is detected, the power saving mode is set i.e., the microprocessor clock rate is divided by e.g., 2 and it's power supply value is decreased by e.g., 3 %. This process can save up to 50% of the power consumption.

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RAM

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M icroprocessor

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Perif 1

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Perif 2

FIGURE 1

1

Power Supply

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ROM

RAM

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Microprocessor

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S E L

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FIGURE 2

Disclosed by International Business Machines Corporation

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