摘要:
A method and apparatus for recovering from a hang condition in a processor having a plurality of execution units. Monitoring is performed to detect a hang condition. Responsive to detecting a hang condition, instructions dispatched to the plurality of execution units are flushed.
摘要:
A method, processor, and data processing system implementing a delayed reject mechanism are disclosed. The processor includes an issue unit suitable for issuing an instruction in a first cycle and a load store unit (LSU). The LSU includes an extend reject calculator circuit configured to receive a set of completion information signals and generate a delay value based thereon. The LSU is adapted to determine whether to reject the instruction in a determination cycle. The number of cycles between the first cycle and the determination cycle is a function of the delay value such that reject timing is variable with respect to the first cycle. In one embodiment, the processor is further configured to reissue the instruction after the determination cycle if the instruction was rejected in the determination cycle. The delay value is conveyed via a 2-bit bus in one embodiment. The 2 bit bus permits delaying the determination cycle from 0 to 3 cycles after a finish cycle. In one embodiment, the number of cycles between the first cycle and the determination cycle includes the number of cycles required to travel a pipeline of the microprocessor plus the number of cycles indicated by the delay value.
摘要:
A multi-mode register rename mechanism which allows a simultaneous multi-threaded processor to support full out-of-order thread execution when the number of threads is low and in-order thread execution when the number of threads increases. Responsive to changing an execution mode of a processor to operate in in-order thread execution mode, the illustrative embodiments switch a physical register in the data processing system to an architected facility, thereby forming a switched physical register. When an instruction is issued to an execution unit, wherein the issued instruction comprises a thread bit, the thread bit is examined to determine if the instruction accesses an architected facility. If the issued instruction accesses an architected facility, the instruction is executed, and the results of the executed instruction are written to the switched physical register.
摘要:
A method of prefetching data in a microprocessor includes identifying a data stream associated with a process and determining a depth associated with the data stream based upon prefetch factors including the number of currently concurrent data streams and data consumption rates associated with the concurrent data streams. Data prefetch requests are allocated with the data stream to reflect the determined depth of the data stream. Allocating data prefetch requests may include allocating prefetch requests for a number of cache lines away from the cache line currently being referenced, wherein the number of cache lines is equal to the determined depth. The method may include, responsive to determining the depth associated with a data stream, configuring prefetch hardware to reflect the determined depth for the identified data stream. Prefetch control bits in an instruction executed by the processor control the prefetch hardware configuration.
摘要:
Recovery circuits react to errors in a processor core by waiting for an error-free completion of any pending store-conditional instruction or a cache-inhibited load before ceasing to checkpoint or backup progress of a processor core. Recovery circuits remove the processor core from the logical configuration of the symmetric multiprocessor system, potentially reducing propagation of errors to other parts of the system. The processor core is reset and the checkpointed values may be restored to registers of the processor core. The core processor is allowed not just to resume execution just prior to the instructions that failed to execute correctly the first time, but is allowed to operate in a reduced execution mode for a preprogrammed number of groups. If the preprogrammed number of instruction groups execute without error, the processor core is allowed to resume normal execution.
摘要:
A method and apparatus for steering instructions dynamically, at issue time, so as to maximize the efficiency of use of execution units being shared by multiple threads being processed by an SMT processor. Resource vectors are used at issue time to redirect instructions, from threads being processed simultaneously, to shared resources for which the multiple threads are competing. The existing resource vectors for instructions that are queued for issuance are analyzed and, where appropriate, dynamically recalculated and modified for maximum efficiency.
摘要:
A method and apparatus are provided for dispatch group checkpointing in a microprocessor, including provisions for handling partially completed dispatch groups and instructions which modify system coherent state prior to completion. An instruction checkpoint retry mechanism is implemented to recover from soft errors in logic. The processor is able to dispatch fixed point unit (FXU), load/store unit (LSU), and floating point unit (FPU) or vector multimedia extension (VMX) instructions on the same cycle. Store data is written to a store queue when a store instruction finishes executing. The data is held in the store queue until the store instruction is checkpointed, at which point it can be released to the coherently shared level 2 (L2) cache.
摘要:
An improved method, apparatus, and computer instructions for grouping instructions. A set of instructions is received for placement into an instruction cache in the data processing system. Instructions in the set of instructions are grouped into a dispatch grouping of instructions prior to the set of instructions being placed in the instruction cache.
摘要:
The present invention allows a microprocessor to identify and speculatively execute future instructions during a stall condition. This allows forward progress to be made through the instruction stream during the stall condition which would otherwise cause the microprocessor or thread of execution to be idle. The execution of such future instructions can initiate a prefetch of data or instructions from a distant cache or main memory, or otherwise make forward progress through the instruction stream. In this manner, when the instructions are re-executed (non speculatively executed) after the stall condition expires, they will execute with a reduced execution latency; e.g. by accessing data prefetched into the L1 cache, or enroute to the processor, or by executing the target instructions following a speculatively resolved mispredicted branch. In speculative mode, instruction operands may be invalid due to source loads that miss the L1 cache, facilities not available in speculative execution mode, or due to speculative instruction results that are not available. Dependency and dirty (i.e. invalid result) bits are tracked and used to determine which speculative instructions are valid for execution. A modified value register storage and bit vector are used to improve the availability of speculative results that would otherwise be discarded once they leave the execution pipeline because they cannot be written to the architected registers. The modified general purpose registers are used to store speculative results when the corresponding instruction reaches writeback and the modified bit vector tracks the results that have been stored there. Younger speculative instructions that do not bypass directly from older instructions will then use this modified data when the corresponding bit in the modified bit vector indicates the data has been modified. Otherwise, data from the architected registers will be used.
摘要:
An apparatus, system and method for quickly determining an oldest instruction in a non-moving instruction queue of a processor are provided. Particularly, instructions are stored, one at a time at a clock cycle, in the non-moving queue. At every clock cycle, a present status of the instructions in the queue is recorded. Using the present status of the instructions in the queue in conjunction with previously recorded statuses of the instructions, the oldest instruction in the queue is determined. The status of the instructions in the queue includes whether or not the instruction has been issued for execution as well as whether or not it is known that the issued instruction has been accepted for execution.