Introduction
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1.4.7System Interrupts
The MCH supports both Intel 8259 and Pentium 4 processor interrupt delivery mechanisms. The serial APIC interrupt mechanism is not supported.
Intel 8259 support consists of flushing inbound hub interface write buffers when an Interrupt Acknowledge cycle is forwarded from the system bus to the hub interface.
The MCH supports the Pentium 4 processor interrupt delivery mechanism. IOxAPIC and PCI MSI interrupts are generated as memory writes. The MCH decodes upstream memory writes to the range
For
1.4.8Powerdown Flow
Since the MCH is powered down during STR, the MCH cannot maintain any state information when exiting STR. Thus, the entire initialization process when exiting STR must be performed by the BIOS via accesses to the DRC2 register.
Entry into STR (ACPI S3) is initiated by the Operating System (OS), based on detecting a lack of system activity. The OS unloads all system device drivers as part of the process of entering STR. The OS then writes to the PM1_CNT I/O register in the ICH2 to trigger the transition into STR.
18 | Intel® 82845 MCH for SDR Datasheet |