Abstract: A circuit includes at least one input, an evaluate pulsed clock, and an output. In one embodiment, the circuit precharges an intermediate node in the circuit in response to a precharge pulsed clock and the evaluate pulsed clock.

Abstract: The present invention provides for executing store instructions with a processor. The present invention executes each of the store instructions by producing the data that is to be stored and by calculating the destination address to which the data is to be stored. In the present invention, the store instructions are executed to produce the destination address of the store instruction earlier than the prior art.

Abstract: A method and apparatus for performing load operations in a computer system. The present invention includes a method and apparatus for dispatching the load operation to be executed. The present invention halts the execution of the load operation when a dependency exists between the load operation and another memory operation currently pending in the system. When the dependency no longer exists, the present invention redispatches the load operation so that it completes.

Abstract: A macro instruction is provided for a microprocessor which allows a programmer to specify a base value, index, scale factor and displacement value for calculating an effective address and returning that result in a single clock cycle. The macro instruction is converted into a micro operation which is provided to the single-cycle execution unit with the required source operands for performing the calculation. Within the single-cycle execution unit, the index and scale factor are provided to a left shifter for multiplying the two values. The result of the left shift operation is added to the sum of the base and displacement. This results in the effective address which is then returned from the single-cycle execution unit to a predetermined destination. This provides for the calculation of an effective address in a single cycle pipeline execution unit that is independent of the memory system execution units.

Abstract: The precharged bit lines of a memory array are provided with corresponding pass gate devices and a common complementary regulation and control circuitry to keep the precharged bit lines at a voltage below a first voltage and to counter-act any leakage to Vcc through a small current drain to a reference voltage. As a result, the voltage on the precharged bit lines are prevented from moving closer to Vcc, even during a prolonged idle period, and failure will not occur, when the memory cells are accessed again after the prolonged idle period.

Abstract: The present invention provides for executing load instructions with a processor having a non-blocking cache memory, wherein individual load operations are dispatched to the cache memory and the cache memory signals the prevent the load operation from being sent to external memory when the load operation misses the cache memory and there is already a currently pending bus cycle to the same cache line. This helps reduce bus traffic on the external bus.

Abstract: A method and apparatus for speculatively dispatching and/or executing LOADs in a computer system includes a memory subsystem of a out-of-order processor that handles LOAD and STORE operations by dispatching them to respective LOAD and STORE buffers in the memory subsystem. When a LOAD is subsequently dispatched for execution, the store buffer is searched for STOREs having unknown addresses. If any STOREs are found which are older than the dispatched LOAD, and which have an unknown address, the LOAD is tagged with an unknown STORE address identification (USAID). When a STORE is dispatched for execution, the LOAD buffer is searched for loads that have been denoted as mis-speculated loads. Mis-speculated loads are prevented from corrupting the architectural state of the machine with invalid data.

Abstract: A computer system having a mechanism for maintaining processor ordering during out-of-order instruction execution is disclosed wherein load memory instructions are accessed according to program order and executed out-of-order in relation to the program order where appropriate. Processors in the system snoop an external bus for bus transactions that conflict with completed load memory instructions before committing results of the completed load memory instructions to an architectural state.

Abstract: A method and apparatus for performing load operations in a computer system. The present invention includes a method and apparatus for dispatching the load operation to be executed. The present invention halts the execution of the load operation when a dependency exists between the load operation and another memory operation currently pending in the system. When the dependency no longer exists, the present invention redispatches the load operation so that it completes.

Abstract: A method and apparatus for performing operations with a processor in a computer system. Load operations are performed by use of a dispatch pipeline and a memory execution pipeline. The dispatch pipeline dispatches the load operation for execution by the processor, while the memory execution pipeline controls the execution of the load operation to memory. The present invention reduces the latency involved in executing a load operation by coupling the execution of the two pipelines during execution of the load operation.

Abstract: A method and apparatus for dispatching load operations in a computer system. The present invention includes a method and apparatus for determining when the load operation is ready for dispatched to memory. The load operation is then scheduled to dispatch from memory and then dispatched to memory. In the present invention, a load is determined ready when it is no longer blocked, such that there is no condition which produces a resource or address dependency causing the load to be blocked.

Abstract: A data cache and a plurality of companion fill buffers having corresponding tag matching circuitry are provided to a computer system. Each fill buffer independently stores and tracks a replacement cache line being filled with data returning from main memory in response to a cache miss. When the cache fill is completed, the replacement cache line is output for the cache tag and data arrays of the data cache if the memory locations are cacheable and the cache line has not been snoop hit while the cache fill was in progress. Additionally, the fill buffers are organized and provided with sufficient address and data ports as well as selectors to allow the fill buffers to respond to subsequent processor loads and stores, and external snoops that hit their cache lines while the cache fills are in progress.

Abstract: A data cache and a plurality of companion fill buffers having corresponding tag matching circuitry are provided to a computer system. Each fill buffer independently stores and tracks a replacement cache line being filled with data returning from main memory in response to a cache miss. When the cache fill is completed, the replacement cache line is output for the cache tag and data arrays of the data cache if the memory locations are cacheable and the cache line has not been snoop hit while the cache fill was in progress. Additionally, the fill buffers are organized and provided with sufficient address and data ports as well as selectors to allow the fill buffers to respond to subsequent processor loads and stores, and external snoops that hit their cache lines while the cache fills are in progress.

Abstract: A method and apparatus for performing store operations that includes calculating the address and obtaining the data for the store operation. The address represents the memory location to which the data is to be stored. Once the address is calculated and the data obtained, the store operation is committed to processor state. The store operation may be dispatched to memory to complete the execution of the store operation.

Abstract: Store forwarding circuitry is provided to an out-of-order execution processor having a store buffer of buffered memory store operations. The store forwarding circuitry conditionally forwards store data for a memory load operation from a variable subset of the buffered memory store operations that is functionally dependent on the time the memory load operation is issued, taking into account the execution states of these buffered memory store operations. The memory load operation may be issued speculatively and/or executed out-of-order. The execution states of the buffered memory store operations may be speculatively executed or committed. The data and address aspects of the memory store operations may be executed separately.

Abstract: In an out-of-order execution computer system, a store buffer is conditionally signaled to output buffered store data of buffered memory store operations, when a buffered memory load operation is being executed. The determination on whether to signal the store buffer or not is made using control information that includes the allocation state of the store buffer at the time the memory load operation being executed was issued. The allocation state includes the identification of the buffer slot storing the last memory store operation stored into the store buffer, and the wraparound state of a circular wraparound allocation approach employed to allocate buffer slots to the memory store operations, at the time the memory load operation being executed was issued.

Abstract: A number of data misalignment detection circuits are provided to select ones of an execution unit and memory order interface components, of an out-of-order (OOO) execution computer system, this aids the buffering and fault generation circuits of the memory order interface components, to buffer and dispatch load and store operations depending on if the misalignments are detected and their nature, resulting in load and store operations of misaligned data against a memory subsystem of the OOO execution computer system are available, the data addressed by the load and store operations are of the following types: chunk split, cache split, or page split misaligned.

Abstract: A charge pump circuit suitable for use in a high frequency phase locked loop. The charge pump circuit comprises a biasing circuit, a charging transistor, a discharging transistor, and a pair of complementary switches. The charging transistor may be a p-channel field effect transistor (FET), and the discharging transistor may be a matched n-channel FET. The drains of the charging and discharging transistors are coupled together to form an output node for the charge pump circuit, and the biasing circuit provides a biasing voltage to the gates of the charging and discharging transistors. A first complementary switch is coupled in series between a supply voltage VCC and the source of the charging transistor. Similarly, a second complementary switch is coupled in series between system ground VSS and the source of the discharging transistor.

Abstract: The data cache unit includes a separate fill buffer and a separate write-back buffer. The fill buffer stores one or more cache lines for transference into data cache banks of the data cache unit. The write-back buffer stores a single cache line evicted from the data cache banks prior to write-back to main memory. Circuitry is provided for transferring a cache line from the fill buffer into the data cache banks while simultaneously transferring a victim cache line from the data cache banks into the write-back buffer. Such allows the overall replace operation to be performed in only a single clock cycle. In a particular implementation, the data cache unit is employed within a microprocessor capable of speculative and out-of-order processing of memory instructions. Moreover, the microprocessor is incorporated within a multiprocessor computer system wherein each microprocessor is capable of snooping the cache lines of data cache units of each other microprocessor. The data cache unit is also a non-blocking cache.

Abstract: A number of identical matching circuits are integrated into the store address buffer, one matching circuit to each buffer slot, for generating a number of match signals, one for each detected match, using at most the entire source address of an instruction being fetched and the corresponding portions of the store destination addresses of the buffered store instructions. Additionally, a stall signal generator complimentary to the store address buffer is provided for generating a single stall signal for the bus controller, using the match signals, thereby stalling an instruction fetch from a source address that is potentially a store destination of one of the buffered store instructions with minimal performance cost.