Abstract: The present invention provides a microprocessor with a special Operation Capture Facility (OCF) mechanism which enables "faulting" whenever there is (a) a memory access request to any one of a specified plurality of blocks of memory (b) a request to access any one of a plurality of specified I-O ports or (c) any one of a specified plurality of interrupts is activated. This OCF mechanism includes a plurality of special registers which store either (a) an I-O port address, (b) a memory address or (c) an interrupt number. Mask registers are provided which (1) mask bits in the special register, thereby providing the ability to fault on an entire block of I-O access requests or upon activation of any one of a block of interrupts and (2) indicate which type of interrupts should be faulted and to indicate whether I-O should be faulted on a byte, word or double word.