Patent ID: 6178495
Filing Date: 2001-01-23
Classification: G06F

Abstract:
A computer processor for performing a function comprising an I-unit that fetches and decodes instruction, an E-unit that executes those instructions, and an interface between the I-unit and the E-unit enabling opcodes to be passed from the I-unit to the E-unit, and E-unit opcode compare logic in the E-unit that compares the opcodes passed to said E-unit by the I-unit and performs actions based on that comparison to modify the function of said computer processor, wherein said E-unit opcode compare logic causes the processor to be serialized after detection of a compared opcode and to transmit said opcode that compared across said interface between the I-unit and the E-unit and back to the I-unit along with an indication of an action to take over; the I-unit upon receipt of said indication of an action to take over begins fetching and decoding instructions again and compares a first instruction that said I-unit decodes against the opcode transmitted to said I-unit by the E-unit, and when said first instruction and the opcode transmitted to said I-unit match the I-unit performs the action indicated to said I-unit by the E-unit, but, if said first instruction and the opcode transmitted to said I-unit do not match, the I-unit executes the first instruction normally and also transmits and indication to the E-unit that said first instruction and the opcode transmitted to said I-unit did not match back over the interface between the I-unit and the E-unit; and said E-unit opcode compare logic contains a latch that is set when a valid opcode compare occurs, that is reset when an instruction completes execution normally, and that is held if the I-unit does not indicate said I-unit detected a mismatch of said first instruction and the opcode transmitted to said I-unit that said I-unit just decoded, said latch being used to temporarily disable the function of said E-unit opcode compare logic when said latch is set, allowing a next instruction to complete execution normally.