Hardware Power Management; System Power Management - NEC VERSA S Service Manual

Hardware Power Management

Specific hardware power management features include the following.
n
Clock stretching — APM reduces the CPU speed without adding a wait state
when a 0.5-cycle wait state is needed in case of DRAM access.
n
Quiet bus — APM inhibits all signals in the AT Bus except the AT bus cycle. This
function saves energy by reducing the number of unnecessary charges and dis-
charges.
n
Power-saving devices — APM puts devices that have power-saving features into
Standby mode when they are not active.

System Power Management

System power management features include the following.
n
APM Idle — APM uses an Idle Detector to sense system inactivity. (The detector
does not work with some applications.)
n
CPU Standby — When enabled, APM slows the CPU clock speed to 3.125 MHz
if no system activity is detected for the specified timeout. Once system activity is
detected, the CPU clock speed returns to normal.
n
Global Standby — When enabled, global standby puts all specified devices into
Standby mode and slows the CPU clock speed to 3.125 MHz after the specified
timeouts. Once system activity is detected, the system returns to normal operation
mode.
n
Auto Suspend — When enabled, Auto Suspend puts the system into Suspend
mode after the specified timeout elapses.
NOTE: System activity includes diskette drive
and hard disk access, keyboard activity, COM
port and LPT port input/output.
Power Management 3-7