© 2011 Advanced Micro Devices, Inc.
46136 AMD RX881 Databook 1.40
Proprietary
6-1
Chapter 6
Power Management and ACPI
6.1
ACPI Power Management Implementation
This chapter describes the support for ACPI power management provided by the RX881. The RX881 Northbridge
supports ACPI
Revision 2.0. The hardware, system BIOS, video BIOS, and drivers of the RX881 have all the logic
required for meeting the power management specifications of PC2001, OnNow, and the Windows Logo Program and
Device Requirements version 2.1.
Table 6-1, “ACPI States Supported by the RX881,”
describes the ACPI states
supported by the RX881.
Table 6-2, “ACPI Signal Definitions,”
describes the signals used in the ACPI power
management scheme of the RX881.
Note:
Also supported are additional processor power states that are not part of the ACPI specification, e.g. C1E (C1
Enhanced) and C3 pop-up. Please refer to the and the
RS880 ASIC Family Register Programming Requirements,
order#
46141, for more information.
Figure 6-1 Linked List for Capabilities
Table 6-1 ACPI States Supported by the RX881
ACPI State
Description
Processor States:
S0/C0: Working State
Working State. The processor is executing instructions.
S0/C1: Halt
CPU Halt state. No instructions are executed. This state has the lowest latency on resume and contributes
minimum power savings.
S0/C2: Stop Grant
Caches Snoopable
Stop Grant or Cache Snoopable CPU state. This state offers more power savings but has a higher latency
on resume than the C1 state.
S0/C3/C1e: Stop Grant
Caches Snoopable
Processor is put into Stop Grant state. Caches are still snoopable. The HyperTransport™ link may be
disconnected and put into a low power state. System memory may be put into self-refresh.
System States:
S3: Standby
Suspend to RAM
System is off but context is saved to RAM. OEM support of this state is optional. System memory is put
into self-refresh.
S4: Hibernate
Suspend to Disk
System is off but context is saved to disk. When the system transitions to the working state, the OS is
resumed without a system re-boot.
S5: Soft Off
System is off. OS re-boots when the system transitions to the working state.
G3: Mechanical Off
Occurs when system power (AC or battery) is not present or is unable to keep the system in one of the
other states.
Table 6-2 ACPI Signal Definitions
Signal Name
Description
Source
ALLOW_LDTSTOP
Output to the Southbridge to allow LDTSTOP# assertion.
Northbridge
LDTSTOP#
HyperTransport™ Technology Stop: Enables and disables links during
system state transitions.
Southbridge
POWERON#
Power On
Power switch
RESET#
Global Reset
Southbridge