FW82801DBM S L6DN Intel, FW82801DBM S L6DN Datasheet - Page 166

• Manufacturer Part Number: FW82801DBM S L6DN
• Manufacturer: Intel

Specifications of FW82801DBM S L6DN

• Lead Free Status / RoHS Status: Not Compliant

Functional Description
5.12.14
5.12.14.1
166
Legacy Power Management Theory of Operation
Instead of relying on ACPI software, legacy power management uses BIOS and various hardware
mechanisms. ICH4 has a greatly simplified method for legacy power management compared with
previous generations (e.g., the PIIX4).
The scheme relies on the concept of detecting when individual subsystems are idle, detecting when
the whole system is idle, and detecting when accesses are attempted to idle subsystems.
However, the OS is assumed to be at least APM enabled. Without APM calls, there is no quick way
to know when the system is idle between keystrokes. The ICH4 does not support the burst modes
found in previous components (e.g., the PIIX4).
APM Power Management
There are additional requirements associated with device power management. To handle this, the
ICH4 has specific SMI# traps available. The following algorithm is used:
The SMI# handler exits with an I/O restart. This allows the original software to continue.
1. The periodic SMI# timer checks if a device is idle for the require time. If so, it puts to the
2. When software (not the SMI# handler) attempts to access the device, a trap occurs (the cycle
3. The SMI# handler turns on the device and turns off the trap
device into a low-power states and sets the associated SMI# trap.
does not really go to the device and an SMI# is generated).
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82801DBM ICH4-M Datasheet