As a former Windows and Linux user, I've been challenged several times to have hardware devices not share some particular IRQ line.
If I understand correctly, IRQ lines are part of the hardware architecture (x86 for example), and Operating Systems (such as OS X) provide some means to configure peripherals and inspect current usage of interrupt lines.
This can be found at
/proc/interrupts on Linux systems and on Device Manager on Windows systems.
Where can I see that information on an OS X? Is it never needed?