Intel IA-32 Manuale Utente

Vol. 3A 17-27

The Pentium Pro processor introduced a new architecture to the IA-32 for handling and
reporting on machine-check exceptions. This machine-check architecture (described in detail in
Chapter 14, “Machine-Check Architecture”) greatly expands the ability of the processor to
report on internal hardware errors.

The priority of exceptions are broken down into several major categories:

1.

Traps on the previous instruction

2.

External interrupts

3.

Faults on fetching the next instruction

4.

Faults in decoding the next instruction

5.

Faults on executing an instruction

There are no changes in the priority of these major categories between the different processors,
however, exceptions within these categories are implementation dependent and may change
from processor to processor.

The following differences in handling interrupts are found among the IA-32 processors.

External hardware interrupts may be recognized on different instruction boundaries on the P6
family, Pentium, Intel486, and Intel386 processors, due to the superscaler designs of the P6
family and Pentium processors. Therefore, the EIP pushed onto the stack when servicing an
interrupt may be different for the P6 family, Pentium, Intel486, and Intel386 processors.   

After an NMI interrupt is recognized by the P6 family, Pentium, Intel486, Intel386, and Intel
286 processors, the NMI interrupt is masked until the first IRET instruction is executed, unlike
the 8086 processor.