10-34 Vol. 3
ADVANCED PROGRAMMABLE INTERRUPT CONTROLLER (APIC)
10.6.3 Error Handling
The local APIC provides an error status register (ESR) that it uses to record errors
that it detects when handling interrupts (see Figure 10-13). An APIC error interrupt
is generated when the local APIC sets one of the error bits in the ESR. The LVT error
register allows selection of the interrupt vector to be delivered to the processor core
when APIC error is detected. The LVT error register also provides a means of masking
an APIC error interrupt.
The ESR is a write/read register. A write (of any value) to the ESR must be done just
prior to reading the ESR to update the register. This initial write causes the ESR
contents to be updated with the latest error status. Back-to-back writes clear the ESR
register. After an error bit is set in the register, it remains set until the register is
cleared.
The functions of the ESR are listed in Tabl e 10 -5.

Figure 10-13. Error Status Register (ESR)

Address: FEE0 0280H
Value after reset: 0H
31 0
Reserved
78123456
Illegal Register Address1
Received Illegal Vector
Send Illegal Vector
Reserved
Receive Accept Error2
Send Accept Error2
Receive Checksum Error2
Send Checksum Error2
2. Only used in the P6 family and Pentium processors;
reserved in Intel Core, Pentium 4 and Intel Xeon processors.
1. Used in Intel Core, Pentium 4, Intel Xeon, and P6 family
processors; reserved in the Pentium processor.
NOTES: