Octagon 6000 Series, User Manual

Page: 141 / 233

18-2
CPU power management 6000 Series user’s manual
In a stand-alone environment (no APM software active), the firmware
works in conjunction with the hardware doze timer and monitoring
functions to identify periods when certain devices or the entire system
are inactive. Individual timers are supported for specific devices, includ-
ing the hard disk. Whenever this device is not accessed for a specified
period, it is powered down to reduce system power consumption. When-
ever none of the monitored system devices has been accessed for a
specified period of time, the performance of the system is reduced or the
CPU is halted altogether to further reduce power consumption.
In a cooperative environment, devices are still controlled by the firm-
ware, but the CPU is never halted without the consent of the APM
software. Rather, the firmware notifies the software when a timer has
expired or some other event has occurred which should place the system
in a reduced power mode. The APM software polls the firmware for
such events. Once an event has occurred, the software initiates the
reduced power mode by acknowledging the event back to the firmware.
The firmware then initiates the reduced power mode. The APM soft-
ware can inquire “APM aware” applications to ensure that the reduced
power mode is acceptable.
≡
Hardware controlled modes
The IDLE timer is configured to reset by specific events which include
the keyboard, video, hard disk, line printer, serial port, floppy disk, and
selected IRQ or DRQ activities. When these specific events do not occur,
the system enters the SUSPEND mode. In this mode, devices such as
the hard disk, floppy disk, parallel port, serial ports, video, super I/O,
and peripheral chip are powered down to conserve power.
In addition to powering down these specified devices, the CPU then
enters the halt state. The hard disk, parallel port, video, real time
clock, IN access, DRQs, GP0 (memory access at E8000h-EFFFFh) and
GP1 (I/O access at 3xxh) are specified events that are configured to
resume the system from the SUSPEND state.
≡
Device power management
The hard disk is power managed on an individual basis. The firmware
configures a hardware timer that is reset each time the device is ac-
cessed. If there is no access to the hard disk, the timer will eventually
expire and the hard disk will then power down to conserve power.
Later, when the hard disk is restored by a triggering event, such as a
keystroke, the access SMI is disabled and the timer is restarted.