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23 22BImportant Technology Information
Kontron User's Guide
coolMonster/PM
52
23.5
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I/O APIC vs. 8259 PIC Interrupt mode
The I/O APIC (Advanced Programmable Interrupt Controller) handles interrupts differently than the
8259 PIC. Enable the I/O APIC mode in the BIOS Setup Utility, if your operating system supports it.
The following information explains these differences to the standard 8259 PIC mode:
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Method of interrupts transmission
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The I/O APIC transmits interrupts through the system bus and interrupts are handled
without the needs for the processor to run an interrupt acknowledge cycle.
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Interrupt priority
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The priority of interrupts in the I/O APIC is independent of the interrupt number.
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More interrupts
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The I/O APIC in the chipset of the coolMONSTER/PM supports a total of 24 interrupts.
Notes
: The APIC is not supported by all operating systems. Only Windows XP supports APIC. The APIC mode must be
enabled in the BIOS setup before the OS installation. APIC only works in ACPI mode.
For more detailed information about APIC, see Chapter 8 of the IA-32 Intel Architecture Software Developer’s
Manual, Volume 3.