Advanced Micro Devices Corporation

Sun Microsystems, Inc.

Chitresh Chandra Narasimhaiah

John Kalamatianos

Marius Evers

Paul S Keltcher

Gary R Lauterbach

Ishwardutt Parulkar

William L Lynch

Dale Robert Greenley

Krishnan V Ramani

Joseph Anthony Petolino, Jr

Alok Garg

David Hugh McIntyre

Sharad Dilip Bade

Senthilkumar Diraviam

A prefetcher maintains the state of stored prefetch information, such as a prefetch confidence level, when a prefetch would cross a memory page boundary. The maintained prefetch information can be used both to identify whether the stride pattern for a particular sequence of demand requests persists after the memory page boundary has been crossed, and to continue to issue prefetch requests according to the identified pattern. The prefetcher therefore does not have re-identify a stride pattern each time a page boundary is crossed by a sequence of demand requests, thereby improving the efficiency and accuracy of the prefetcher.

Stride prefetching across memory pages

Methods and systems for prefetching data for a processor are provided. A system is configured for and a method includes selecting one of a first prefetching control logic and a second prefetching control logic of the processor as a candidate feature, capturing the performance metric of the processor over an inactive sample period when the candidate feature is inactive, capturing a performance metric of the processor over an active sample period when the candidate feature is active, comparing the performance metric of the processor for the active and inactive sample periods, and setting a status of the candidate feature as enabled when the performance metric in the active period indicates improvement over the performance metric in the inactive period, and as disabled when the performance metric in the inactive period indicates improvement over the performance metric in the active period.

Dynamic evaluation and reconfiguration of a data prefetcher

A method and a processor load/store unit (LSU) are described for performing store-to-load forwarding (STLF) from an interlocking store. STLF is performed when a starting address of the store and the load do not match, or when a data size of the store is smaller than a data size of the load. The LSU detects a load that interlocks with a store, and determines whether all or only a portion of data bytes needed by the load can be provided by the interlocking store. If it is determined that only a portion of the data bytes needed by the load can be provided by the interlocking store, then that portion of the data bytes is provided by a store data buffer (SDB) and the remaining portion of the data bytes needed by the load is provided by a data cache (DC). Otherwise, the SDB provides all of the data bytes.

Method and apparatus for performing store-to-load forwarding from an interlocking store using an enhanced load/store unit in a processor

A method and apparatus for stopping the internal clock of a microprocessor synchronously with the execution of an instruction is provided. A stop instruction is placed in a sequence of instructions to be executed by the microprocessor. The execution of the stop execution may store a stop value into a stop register of the microprocessor. Clock stop logic detects when the stop value has been stored into the stop register. The clock stop logic instructs a clock generation component, of the microprocessor, to cease generation of an internal clock signal, thereby preventing the microprocessor from changing state. As further instructions are not executed by the microprocessor, the state of the microprocessor reflects the execution of the instruction immediately prior to the stop instruction. The processing state of the microprocessor may be obtained for use in debugging the design of the microprocessor or the instructions executed thereby.

Mechanism to stop instruction execution at a microprocessor

A system for on-chip testing of embedded memories using Address Space Identifier (ASI) bus in Scalable Processor ARChitecture (SPARC) microprocessors. An integrated circuit includes a plurality of memory arrays, Address Space Identifier (ASI) bus interface logic connected by an ASI bus to the plurality of memory arrays, and a memory control unit and a memory built-in self-test (MBIST) engine connected to the ASI bus interface logic. Rather than direct access, the MBIST engine utilizes the ASI bus interface logic and the ASI bus to perform memory testing. The MBIST engine, programmed with memory array parameters, includes a programmable state machine controller to which is connected a programmable data generator, a programmable address generator, and a programmable comparator. The data generator provides data as appropriate. The address generator provides addresses as appropriate. The comparator provides test results information for the particular test situation. The MBIST engine generates a test status output.

On-chip testing of embedded memories using Address Space Identifier bus in SPARC architectures

The present invention solves the problems associated with the prior art by providing a latency prediction bit (LPB) to indicate the latency with which an instruction should be executed, implicitly indicating whether a data dependency is likely to exist and the likelihood of that dependency causing a hazard. In a processor according to the present invention, an instruction dependent upon a given LDI instruction is issued a given number of machine cycles after that LDI instruction, the number of machine cycles being based on the value of the LPB associated with that LDI instruction. The LPB's value, in turn, depends on whether data will need to be forwarded to the functional unit involved during the execution of LDI instruction. The ability to predict such hazards is important in maintaining a pipeline's throughput and avoiding unnecessary recirculations.

Growing community of inventors

San Jose, CA, United States of America

Chitresh Chandra Narasimhaiah