Abstract: A method of instruction issue (3200) in a microprocessor (1100, 1400, or 1500) with execution pipestages (E1, E2, etc.) and that executes a producer instruction Ip and issues a candidate instruction I0 (3245) having a source operand dependency on a destination operand of instruction Ip. The method includes issuing the candidate instruction I0 as a function (1720, 1950, 1958, 3235) of a pipestage EN(I0) of first need by the candidate instruction for the source operand, a pipestage EA(Ip) of first availability of the destination operand from the producer instruction, and the one execution pipestage E(Ip) currently associated with the producer instruction. A method of data forwarding (3300) in a microprocessor (1100, 1400, or 1500) having a pipeline (1640) having pipestages (E1, E2, etc.

Abstract: A processor (1700) including a pipeline (1710, 1740) having a fetch pipeline (1710) with branch prediction circuitry (1840) to supply respective predicted taken target addresses for branch instructions, an execution pipeline (1740) with a branch execution circuit (1870), and storage elements (in 1860) and control logic (2350) operable to establish a first-in-first-out (FIFO) circuit (1860) with a write pointer WP1 and a read pointer RP1. The control logic (2350) is responsive to the branch prediction circuitry (1840) to write a predicted taken target address to a storage element (in 1860) identified by the write pointer (WP1) and the predicted taken target address remains stationary therein. The FIFO circuit (1860) bypasses a plurality of pipestages between the branch prediction circuitry (1840) and the branch execution circuit (1870). The control logic (2350) is operable to read a predicted taken target address (PTTPCA) from a storage element (in 1860) identified by the read pointer RP1.

Abstract: A system and method for power efficient memory caching. Some illustrative embodiments may include a system comprising: a hash address generator coupled to an address bus (the hash address generator converts a bus address present on the address bus into a current hashed address); a cache memory coupled to the address bus (the cache memory comprises a tag stored in one of a plurality of tag cache ways and data stored in one of a plurality of data cache ways); and a hash memory coupled to the address bus (the hash memory comprises a saved hashed address, the saved hashed address associated with the data and the tag). Less than all of the plurality of tag cache ways are enabled when the current hashed address matches the saved hashed addresses. An enabled tag cache way comprises the tag.

Abstract: Tunable external cavity lasers are used in applications such as interferometry, FM spectroscopy, and optical communications equipment testing. Mode hop free high bandwidth frequency modulation operation is desired in a tunable external cavity laser. This application describes new and novel techniques for controlling the output wavelength of a tunable external cavity laser while suppressing mode hop.

Abstract: Methods and apparatus are provided for issuing instructions in a processor having a pipeline. A method includes providing a loop buffer for holding program loop instructions and a register file for holding loop control parameters; in response to decoding of a first loop setup instruction, marking a first entry in the register file as a current entry and writing in the first entry loop control parameters represented in the first loop setup instruction; marking the current entry in the register file as an architectural entry in response to the first loop setup instruction being committed; and sending a loop bottom indicator down the pipeline with a loop bottom instruction.

Abstract: A security device for attaching laptop computers and the like to a desk includes a body portion which is to be received in an aperture of the work surface of a work station or desk. The body portion includes a grommet which fits within the aperture with a flange at the top. A lock plate bears against the underside of the work surface to hold the grommet in place. A combination of pawls and lock teeth hold the lock plate in place. Within the grommet there is a cable lock to which the computing device is attached.

Abstract: An instruction alignment unit is provided which is capable of routing variable byte length instructions simultaneously to a plurality of decode units which form fixed issue positions within a superscalar microprocessor. The instruction alignment unit may be implemented with a relatively small number of cascaded levels of logic gates, thus accomodating very high frequencies of operation. In one embodiment, the superscalar microprocessor includes an instruction cache for storing a plurality of variable byte-length instructions and a predecode unit for generating predecode tags which identify the location of the start byte of each variable byte-length instruction. An instruction alignment unit is configured to channel a plurality of the variable byte-length instructions simultaneously to predetermined issue positions depending upon the locations of their corresponding start bytes in a cache line.

Abstract: An instruction alignment unit is provided which is capable of routing variable byte length instructions simultaneously to a plurality of decode units which form fixed issue positions within a superscalar microprocessor. The instruction alignment unit may be implemented with a relatively small number of cascaded levels of logic gates, thus accomodating very high frequencies of operation. In one embodiment, the superscalar microprocessor includes an instruction cache for storing a plurality of variable byte-length instructions and a predecode unit for generating predecode tags which identify the location of the start byte of each variable byte-length instruction. An instruction alignment unit is configured to channel a plurality of the variable byte-length instructions simultaneously to predetermined issue positions depending upon the locations of their corresponding start bytes in a cache line.

Abstract: A superscalar microprocessor having an instruction alignment unit, an instruction cache, a plurality of decode units and a predecode unit is provided. The instruction alignment unit transfers a fixed number of instructions from the instruction cache to each of the plurality of decode units. The instructions are selected from a quantity of bytes according to a predecode tag generated by the predecode unit. The predecode tag includes start-byte bits that indicate which bytes within the quantity of bytes are the first byte of an instruction. The instruction alignment unit independently scans a plurality of groups of instruction bytes, selecting start bytes and a plurality of contiguous bytes for each of a plurality of issue positions. Initially, the instruction alignment unit selects a group of issue positions for each of the plurality of groups of instructions.

Abstract: A self-timed and self-enabled distributed clock is provided for pipeline processor design having functional blocks which include one or more pipeline stages for processing instructions and operations. Each pipeline stage of the processor includes self-timed logic and an enable signal to set up the valid data input to the next pipeline stage. The self-timed logic is used instead of a central, synchronous clock having a predetermined period and provides flexibility of expanding or contracting the clock period in multiple time units depending on the functionality of each pipeline stage. The interfacing between the pipeline stages is handled by a queue buffer which stores incoming instructions to keep the pipeline fully occupied any time there are instructions in the pipeline. A functional unit and its distributed clock are activated only if there is instruction in the pipeline and is otherwise idle.

Abstract: A superscalar microprocessor implements instruction level patching. A instruction fetch unit includes a register for storing opcodes of instructions to be patched. When an instruction is fetched, the instruction fetch unit compares the opcode of the fetched instruction to the opcode stored in the patch opcode register. If the opcode of the fetched instruction matches an opcode stored in the patch opcode register, the instruction is dispatched to a microcode instruction unit. The microcode instruction unit invokes a patch microcode routine that dispatches a plurality of microcode instruction that causes a substitute microcode instruction stored in external memory to be loaded into patch data registers. The microcode instruction unit then dispatches the substitute instruction stored in the patch data registers and the substitute instruction is executed by a functional unit in place of the original instruction.

Abstract: An instruction alignment unit is provided which is capable of routing variable byte length instructions simultaneously to a plurality of decode units which form fixed issue positions within a superscalar microprocessor. The instruction alignment unit may be implemented with a relatively small number of cascaded levels of logic gates, thus accomodating very high frequencies of operation. In none embodiment, the superscalar microprocessor includes an instruction cache for storing a plurality of variable byte-length instructions and a predecode unit for generating predecode tags which identify the location of the start byte of each variable byte-length instruction. An instruction alignment unit is configured to channel a plurality of the variable byte-length instructions simultaneously to predetermined issue positions depending upon the locations of their corresponding start bytes in a cache line.

Abstract: A high performance superscalar microprocessor including an instruction alignment unit is provided which is capable of routing variable byte length instructions simultaneously to a plurality of decode units which form fixed issue positions within the superscalar microprocessor. The instruction alignment unit may be implemented with a relatively small number of cascaded levels of logic gates, thus accommodating very high frequencies of operation. In one embodiment, the superscalar microprocessor includes an instruction cache for storing a plurality of variable byte-length instructions and a predecode unit for generating predecode tags which identify the location of the start byte of each variable byte-length instruction. An instruction alignment unit is configured to channel a plurality of the variable byte-length instructions simultaneously to predetermined issue positions depending upon the locations of their corresponding start bytes in a cache line.

Abstract: A data latching mechanism uses Column Address Strobe (CAS) signals to effect one-cycle DRAM page-mode access at high operation frequency.

Abstract: An instruction alignment unit is provided which transfers a fixed number of instructions from an instruction cache to each of a plurality of decode units. The instructions are selected from a quantity of bytes according to a predecode tag generated by a predecode unit. The predecode tag includes start-byte bits that indicate which bytes within the quantity of bytes are the first byte of an instruction. The instruction alignment unit independently scans a plurality of groups of instruction bytes, selecting start bytes and a plurality of contiguous bytes for each of a plurality of issue positions. Initially, the instruction alignment unit selects a group of issue positions for each of the plurality of groups of instructions. The instruction alignment unit then shifts and merges the independently produced issue positions to produce a final set of issue positions for transfer to a plurality of decode units.

Abstract: A cache memory system features a combination instruction cache and prefetch buffer, which obviates any requirement for a bus interconnecting the cache and buffer and which also effectively allows the instruction buffer to write data into the cache with improved utilization of prefetched instructions and with decreased use of power and silicon space.

Abstract: An latch circuit includes an input line receiving electrical signals from a bus, a latch for conducting electrical signals from the precharged bus to a receiving circuit, and a structure for enabling the latch only when data is driven onto the bus.