Windows® Internals, Sixth Edition, Part 1

Windows maps hardware IRQs to interrupt numbers in the IDT, and the system also uses the IDT to configure trap handlers for exceptions. For example, the x86 and x64 exception number for a page fault (an exception that occurs when a thread attempts to access a page of virtual memory that isn’t defined or present) is 0xe (14). Thus, entry 0xe in the IDT points to the system’s page-fault handler. Although the architectures supported by Windows allow up to 256 IDT entries, the number of IRQs a particular machine can support is determined by the design of the interrupt controller the machine uses.

EXPERIMENT: Viewing the IDT

You can view the contents of the IDT, including information on what trap handlers Windows has assigned to interrupts (including exceptions and IRQs), using the !idt kernel debugger command. The !idt command with no flags shows simplified output that includes only registered hardware interrupts (and, on 64-bit machines, the processor trap handlers).