82371AB Datasheet, PDF (228/284 Pages) Intel Corporation – PCI-TO-ISA / IDE XCELERATOR PIIX4

82371AB (PIIX4)
E
11.4. Suspend/Resume and Power Plane Control
11.4.1. SYSTEM SUSPEND
PIIX4 supports three different Suspend modes. The PIIX4 power management architecture is designed to allow
a single system to support multiple suspend modes and to switch between those modes as required. A
suspended system can be resumed via a number of different events. It will then return to full operation where it
can continue processing or be placed into another suspend mode (potentially a lower power mode than it
resumed from).
The standard system usage model for these modes are described here and include Power On Suspend (POS),
Suspend to RAM (STR), and Suspend to Disk (STD). This definition allows for other system usage models
which use the PIIX4 suspend/resume control signals in other ways. The standard system mode names are used
throughout this document. Table 34 summarizes these modes along with their target
system power.
Power On Suspend (POS) System Model
All devices are powered up except for the clock synthesizer. The Host and PCI clocks are inactive and PIIX4
provides control signals and 32-kHz Suspend Clock (SUSCLK) to allow for DRAM refresh and to turn off the
clock synthesizer. The only power consumed in the system is due to DRAM Refresh and leakage current of the
powered devices.
When the system resumes from POS, PIIX4 can optionally resume without resetting the system, can reset the
processor only, or can reset the entire system. When no reset is performed, PIIX4 only needs to wait for the
clock synthesizer and processor PLLs to lock before the system is resumed. This takes typically 20 ms.
Suspend to RAM (STR)
Power is removed from most of the system components during STR, except the DRAM. Power is supplied to
Suspend Refresh logic in the Host Controller, and RTC and Suspend Well logic in PIIX4. PIIX4 provides control
signals and 32-kHz Suspend Clock (SUSCLK) to allow for DRAM refresh and to turn off the clock synthesizer
and other power planes.
PIIX4 will reset the system on resume from STR.
Suspend to DISK (STD)
Power is removed from most of the system components during STD. Power is maintained to the RTC and
Suspend Well logic in PIIX4.
PIIX4 will reset the system on resume from STD.
This state is also called the Soft Off (SOff) state. The difference depends on whether the system state is
restored by software to a pre-suspend condition or if the system is rebooted.
Mechanical Off (MOff)
This is not a suspend state. This is a condition where all power except the RTC battery has been removed from
the system. It is typically controlled by a mechanical switch turning off AC power to a power supply.
It could be used as a condition in which a mobile system’s main battery has been removed.
228
PRELIMINARY
4/9/97 2:23 PM PIIX4aDS
INTEL CONFIDENTIAL
(until publication date)