Aaeon SBC-555 Manual page 48

The following four modes are Green PC power saving functions
which are only user configurable when User Defind Power
Management has been selected. See above for available selec-
tions.
HDD Off After
When enabled and after the set time of system inactivity, the hard
disk drive will be powered down while all other devices remain
active.
Doze Mode
When enabled and after th eset time of system inactivity, th eCPU
clock will run at slower speed while all other devices still operate
at full speed.
Standby Mode
When enabled and after the set time of system inactivity, the fixed
disk drive and the video would be shut off while all other devices
still operate at full speed.
Suspend Mode
When enabled and after the set time of system inactivity, all
devices except the CPU will be shut off.
PM events are I/O events whose occurrence can prevent the
system from entering a power saving mode or can awaken the
system from such a mode. In effect, the system remains alert for
anything which occurs to a device which is configured as Enabled,
even when the system is in a power down mode.
The following is a list of IRQ, Interrupt ReQuests, which can be
exempted much as the COM ports and LPT ports above can.
When an I/O device wants to gain the attention of the operating
system, it signals this by causing an IRQ to occur. When the
operating system is ready to respond to the request, it interrupts
itself and performs the service.