Abstract: The invention relates to a method for issuing instructions in a processor. In one version of the invention, the method includes the steps of dispatching the instruction and source information to a queue, determining validity of the source information, and issuing the instruction for execution in response to the source information validity.

Abstract: During operation of a pipelined data processing system, an interruptible instruction table is used to store target identifiers associated with instructions which may result in speculative execution. During operation of the interruptible instruction table, a pointer, referred to as a completing instruction buffer entry pointer, points to a bottom of the interruptible instruction table if that table includes any instruction. An entry at the bottom of the interruptible instruction table is a next instruction to complete. This entry includes a target identifier, referred to as a non-speculative-non-interruptible TID, may be used to release resources held for all prior executed instructions. The data processing system determines the value of the non-speculative-non-interruptible TID to ensure that order determination is preserved and provides a true speculative execution point.

Abstract: In a method and apparatus for allocating processor resources in a data processing system, instructions are dispatched and tagged for processing. A processor resource snoops to obtain execution results for the tagged instructions. Such an instruction is logically "finished" in response to determining that it will not cause an interrupt (which includes not changing the sequence of completing instructions), and "completed" in response to finishing all earlier dispatched instructions. Information is entered for such an instructions in rename buffer in response to the instruction targeting an architected register, and such a rename buffer entry is released in response to completing the entry's instruction. The rename buffer may comprise a history buffer. Also, information for the instructions is entered in a completion queue in response to dispatching the instructions, and the queue entry for such an instruction is released in response to completion of the instruction.

Abstract: The invention includes a method and apparatus for maintaining content of predefined registers of a processor which uses the registers for executing instructions, including an interruptible instruction. According to the invention, instructions are dispatched, including instructions ("targeting instructions") which target registers for holding register content, and an interruptible instruction. The content of a register is altered in response to executing a targeting instruction. An entry of register content is stored only for selected ones of the dispatched targeting instructions.

Abstract: The present invention is directed to a method and apparatus for dispatching instructions in an information handling system. A pre-execution queue stores instructions, and at least one execution cluster is operably coupled to the pre-execution queue. An execution cluster comprises an early execution unit for executing a first instruction dispatched from the pre-execution queue to generate and forward a first result and a late execution unit for executing a second instruction dispatched from the pre-execution queue to generate and forward a second result after the first execution unit forwards the first result. The invention further includes circuitry operably associated with the pre-execution queue, and a method for prioritizing the order in which the instructions in the pre-execution queue are dispatched to the execution cluster.

Abstract: A method and apparatus for maintaining content of registers of a processor which uses the registers for processing instructions. Entries are stored in a buffer for restoring register content in response to an interruption by an interruptible instruction. Entries include information for reducing the number of entries selected for the restoring. A set of the buffer entries is selected, in response to the interruption and the information, for restoring register content. The set includes only entries which are necessary for restoring the content in response to the interruption so that the content of the processor registers may be restored in a single processor cycle, even if multiple entries are stored for a first one of the registers and multiple entries are stored for a second one of the registers.

Abstract: An information handling system includes an instruction unit, one or more execution units, a memory management unit, connected to the instruction unit, to a memory system, a cache management unit, one or more levels of cache memory associated with the one or more execution units, one or more I/O controllers connected to a bus which connects to the execution units and to the memory systems and to cache, and a completion unit for tracking sequence of instruction dispatch and instruction completion. The completion unit includes a Content Addressable Register Buffer Assignment Table, a Register Status Table, an Instruction Queue, and a Completion Table to control order of execution and completion of instructions in a sequence dependent on availability of operands.

Abstract: The present invention is related to a circuit useful to manage a random order queue having a plurality of queue entries, each queue entry having an associated validity bit which indicates whether the queue entry contains valid data. In one embodiment, the circuit includes a first plurality of inputs for receiving validity signals responsive to a first group of validity bits, a second plurality of inputs for receiving shift signals responsive to a second group of validity bits, and a plurality of outputs for providing select signals to multiplexers coupled to the queue, the select signals being responsive to the shift signals and the validity signals.

Abstract: A data processor assigns a unique identifier to each instruction. As there are a finite number of unique identifiers, the identifiers are reused during execution of a program within the data processing system. To maintain an age relationship between instructions executing in the pipeline processor, a methodology is developed to ensure that reused identifiers are properly designated as being younger than their older but larger in magnitude, counterparts. To resolve this issue, assume that the identifier assigned to each instruction has N bits, and therefore, there are 2.sup.N identifiers to be assigned to instructions in the program. The 2.sup.N identifiers are separated into 2.sup.m banks. In addition to assigning identifiers to each instruction, an identifier assignment logic circuit within the pipeline processor provides a global signal that indicates which bank is a youngest bank from which the identifiers are assigned to a remaining portion of the pipeline processor.

Abstract: Logic circuitry provides a fast resolution of conditional branch instructions in a high-performance superscalar processor. The logic circuitry facilities early (fast) resolution of a subset of conditional branches located within the first position of the primary instruction buffer within the processor enabling the overall branch processing logic to bypass history table-based prediction logic for such branches without crossing the cycle boundary. Thus, penalties associated with possible mispredictions for this subset of conditional branches are avoided.

Abstract: In a data processing system using a number of registers for processing instructions, a method and apparatus for writing information to the registers. Ports are accessed for writing back to processor registers, information ("results") resulting from and associated with executing instructions. Certain of the results are stored for restoring to the registers. In response to an interruption at least one of the ports is accessed for restoring stored results to the registers. Accesses to the ports are arbitrated in response to comparing writeback and restoration results. A result includes identification of the instruction the result is associated with (a "TID"), and a register that is targeted by the result (a "TR"). The comparing includes comparing TID's and TR's for the results.

Abstract: The present invention is directed to an apparatus and method for sending and receiving instructions, or operations, in an information handling system. The operations are received in a particular, desired order, regardless of the order in which the operations are sent. The invention provides an apparatus and method which assigns a vector to each operation or sub-operation to indicate the desired receiving order of the operations. In addition, the apparatus and method implementing the invention assign a vector to the receiving unit to indicate the order into which the operations should be placed in the receiving unit. The two vectors are manipulated in such a way as to signal which operations should be accepted into which places in the receiving unit. One operation may be mapped to multiple sub-operations in the receiving unit.

Abstract: Control circuitry is used to select M entries from an N-entry storage array by viewing the array from both ends. Beginning at both ends of the array, particular bit values or entry content is looked for by the control logic. Once found at both ends, these entries are then used to produce control signals to be sent to a pair of muxes to remove these entries. Then a subset of the original array consisting of the remaining entries of the array is then iterated upon by a similar set of control circuitry for finding and removing the next M entries from the storage array.

Abstract: Two processor controls for supporting efficient Firm Consistency while allowing out-of-order execution of Load instructions is provided. The Touch control operates when the processor stores a subsequent Store in a pending Store buffer while awaiting any outstanding Loads or Stores. The efficiency of the pending Store is improved by issuing a Touch of the data which pre-loads the line of data in the cache that is the subject of the store. The processor can complete out-of-order execution of a subsequently issued Load relative to a prior Load, but only to its finished state. The subsequently issued Load is not allowed to complete until the prior Load is completed. The Finished Load Cancellation control ensures that Firm Consistency is maintained by canceling any finished Loads, and subsequent instructions, when the subject of the Load is the same as an invalidation request from a multiprocessor.