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Functional Architecture
Intel® Server Board SE7520AF2 TPS
56
Revision
1.2
Intel order number C77866-003
3.4.2.1
Legacy Interrupt Routing
For PC-compatible mode, the ICH5-R provides two 82C59-compatible interrupt controllers. The
two controllers are cascaded with interrupt levels 8-15 entering on level 2 of the primary
interrupt controller (standard PC configuration). A single interrupt signal is presented to the
processors, to which only one processor will respond for servicing. The ICH5-R contains
configuration registers that define which interrupt source logically maps to I/O APIC INTx pins.
Interrupts, both PCI and IRQ types, are handled by the ICH5-R. The ICH5-R then translates
these to the APIC bus. The numbers in the table below indicate the ICH5-R PCI interrupt input
pin to which the associated device interrupt (INTA, INTB, INTC, and INTD) is connected. The
ICH5-R’ I/O APIC exists on the I/O APIC bus with the processors.
Table 18. PCI Interrupt Routing/Sharing
Interrupt
INT A
INT B
INT C
INT D
USB Controller 1 and 4
ICH5R_PIRQA
USB Controller 1
ICH5R_PIRQH
USB Controller 2
ICH5R_PIRQD
USB Controller 3, IDE, SATA
ICH5R_PIRQC
Video ICH5R_PIRQB
SIO ICH5R_SERIRQ
Legacy IDE
ICH5R_IRQ14
82546GB 1
PXH_PBIRQ4
82546GB 2
PXH_PBIRQ5
SCSI Controller 1
IOP_XINT0
SCSI Controller 2
IOP_XINT1
Slot 1 (PCI-X 64/133)
IOP_XINT4
IOP_XINT5 IOP_XINT6 IOP_XINT7
Slot 3 (PCI EXP x4)
NA
NA
NA
NA
Slot 4 (PCI EXP x8)
NA
NA
NA
NA
Slot 5 (PCI-X 64/133)
PXH_PAIRQ0
PXH_PAIRQ1 PXH_PAIRQ2 PXH_PAIRQ3
Slot 6 (PCI-X 64/100)
PXH_PBIRQ0
PXH_PBIRQ1 PXH_PBIRQ2 PXH_PBIRQ3
Slot 6 (Upper slot of optional 2-
slot riser)
PXH_PBIRQ0 PXH_PBIRQ1 PXH_PBIRQ2 PXH_PBIRQ3
Slot 7 (Lower slot of optional 2-
slot riser)
PXH_PBIRQ0 PXH_PBIRQ1 PXH_PBIRQ2 PXH_PBIRQ3
3.4.2.2
APIC Interrupt Routing
For APIC mode, the Intel® Server Board SE7520AF2 interrupt architecture incorporates three
Intel I/O APIC devices to manage and broadcast interrupts to local APICs in each processor.
The Intel I/O APICs monitor each interrupt on each PCI device including PCI slots in addition to
the ISA compatibility interrupts IRQ(0-15). When an interrupt occurs, a message corresponding
to the interrupt is sent across a three-wire serial interface to the local APICs. The APIC bus
minimizes interrupt latency time for compatibility interrupt sources. The I/O APICs can also
supply greater than 16 interrupt levels to the processor(s). This APIC bus consists of an APIC
clock and two bidirectional data lines.