Intel Corporation

Nimish H Modi

Derrick Chu Lin

Donald B Alpert

Robert S Dreyer

Ed Grochowski

Syed A Zaidi

Bharat N Zaveri

Mike J Tripp

Ramamohan Rao Vakkalagadda

Varsha P Tagare

Satchitanand Jain

Charkravaythy Kosaraju

Champa R Yellamilli

A technique for increasing the number of physical segment registers by renaming logical segment registers into a larger register space. The remapping of the segment registers allows for instructions accessing the segment registers to be executed non-serially. The renaming of segment registers is achieved by assigning a shadow register to a segment register name. Thus, a pair of registers are physically available for a specified logical register in an instruction set to be renamed. Two bits, designated as the PSEG and SPEC bits, are used to control the remapping.

System for allowing multiple instructions to use the same logical

A microprocessor that handles invalid opcodes via an event-signaling micro-operation is disclosed. The microprocessor comprises a decoder that decodes macroinstructions, including an opcode, into a single microprocessor cycle micro-operation. The decoder detects invalid opcodes and replaces the invalid opcodes with an event-signaling micro-operation that triggers an invalid opcode assist. The invalid opcode assist triggers an invalid opcode exception handler that processes the invalid opcode.

Method and apparatus for handling invalid opcode faults via execution of

A microprocessor is disclosed herein having an external command mode for directly accessing the execution unit, responsive to externally generated commands and instructions. An external instruction path is provided, as well as a conventional processor-driven instruction path. A multiplexer is provided that selects which of the instruction paths is actually supplied to the execution unit. Using the external command mode, the user can examine and modify registers, memory, and I/O space without otherwise affecting their contents. Any instruction executable by the execution unit is executable in the external command mode. Because direct access is provided into the execution unit, there is no implicit updating that would otherwise affect the state of the processor and require saving to an alternate memory. The present invention is implemented with a conventional test access port designed in accordance with the IEEE 1149.1 boundary scan standard, with modification to include an instruction register, a data register, and control logic. The external command mode is applicable to single and multiple pipeline processors. The circuit described herein includes several selectors for selecting between the probe mode and the processor-driven mode of operation, including an external pin, an external command, and a debug exception. For ascertaining if the circuit is in the external command mode, an acknowledge pin is provided to indicate when the execution unit is ready to accept an instruction in the probe model.

Microprocessor with an external command mode for diagnosis and debugging

Apparatus for increasing the decoding speed of a microprocessor. The apparatus includes a first decoder for decoding macroinstructions. The first decoder includes apparatus for generating a single initial microinstruction vector from simple macroinstructions and from complex macroinstructions having a beginning microinstruction equivalent to a microinstruction for a simple macroinstruction. The first decoder also includes apparatus for indicating a beginning address for generating any remaining microinstruction vectors for a complex macroinstruction decoded by the first decoder. The apparatus for increasing the decoding speed of a microprocessor also includes apparatus, coupled to the first decoder, for generating any remaining microinstruction vectors for complex macroinstructions decoded by the first decoder. The apparatus for generating any remaining microinstruction vectors includes apparatus for responding to the apparatus for indicating a beginning address.

Method and apparatus for increasing the decoding speed of a

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San Jose, CA, United States of America

Nimish H Modi