Oops,
 > Bernhard is totally correct at the processor level for
 > the 80x86 family.
 > Most of the processors in the family only have two interrupt lines, NMI
 > and INTR
    Correct, but this is where you started losing me, George. Intel 
interrupts are as simple as Zilog ones. Software interrupts were new, but 
they're a bonus.
    There are 256 real mode interrupts
    There are NMI
    There are protected mode virtual interrupts.
    These loosely corresposnd to Mode 0, NMI and Mode 2 for the old eight bit 
efforts, don't they? PICs and PITs aren't built in to the CPU; they are 
peripheral.
    Maybe the PC orientation of the original question has influenced your 
answer. I certainly remember interrupt descriptor tables and an IDT base. Is 
my memory playing tricks again?
    Let us also dispel the nonsense that interrupts are somehow off-topic for 
the C Echo. The C language has to try to cope with all three sorts of 
interrupt if it is maintain any pretence at being a system language. 
Processor specifics can be better dealt with in processor specific echoes, 
but those are disappearing fast. :-)
Best wishes,
Bill.
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