The Unabridged Pentium 4 IA32 Processor Genealogy

Interrupt/Exception Priority

It should be fairly obvious that the processor can only execute one program at a time. This being the case, if multiple interrupts and/or exception conditions occurred simultaneously, the processor must decide in what order to service the simultaneous events.

The IA32 processor family divides the possible types of interrupts and exceptions into five classes (listed in Table 14-4 on page 266). Class one is the highest priority group, while class eight is the lowest (the 386 only defined classes 1 through 5). Please note that the table reflects the classes defined as of this writing. The processor services the exception or interrupt from the highest class first. Lower priority exceptions are discarded, while lower priority ...