International Business Machines Corporation

Duane Arlyn Averill

John Michael Borkenhagen

David Alan Shedivy

Joseph Allen Kirscht

Herman Lee Blackmon

Russell Dean Hoover

Richard James Eickemeyer

Sheldon Bernard Levenstein

Andrew Henry Wottreng

Philip Rogers Hillier, Iii

Sandra S Woodward

James A Steenburgh

Christopher Tung Phan

Corey Virgil Swenson

Martha Ellen Voytovich

Sharon Denos Vincent

James Ira Brookhouser

In a method of managing a cache directory in a memory system, an original system address is presented to the cache directory when corresponding associativity data is allocated to an associativity class in the cache directory. The original system address is normalized by removing address space corresponding to a memory hole, thereby generating a normalized address. The normalized address is stored in the cache directory. The normalized address is de-normalized, thereby generating a de-normalized address, when the associativity data is cast out of the cache directory to make room for new associativity data. The de-normalized address is sent to the memory system for coherency management.

Method for increasing cache directory associativity classes in a system with a register space memory

In a method of generating a cache directory to include a plurality of associativity classes, each associativity class includes an address tag including a plurality of address bits. Each address tag is configured to store a unique address to a specific location in an memory space. An amount of memory that is in an actually configured portion of the memory space is determined. A minimum number of bits necessary to address each memory location in the actually configured portion of the memory space is determined. Each address tag is configured in each associativity class to include the minimum number of bits necessary to address each memory location in the actually configured portion of the memory space. The cache directory is configured to include a maximum number of associativity classes per line in the cache directory.

Method for increasing cache directory associativity classes via efficient tag bit reclaimation

A method for allowing simultaneous parameter-driven and deterministic simulation during verification of a hardware design, comprising: enabling a plurality of random parameter-driven commands from a random command generator to execute in a simulation environment during verification of the hardware design through a command managing device; and enabling a plurality of deterministic commands from a manually-driven testcase port to execute in the simulation environment simultaneously with the plurality of random parameter-driven commands during verification of the hardware design through the command managing device, the plurality of deterministic commands and the plurality of random parameter-driven commands each verify the functionality of the hardware design.

Simultaneous parameter-driven and deterministic simulation with or without synchronization

A computer system includes multiple caches and a cache line state directory structure, having at least a portion dedicated to a particular device cache within a particular device, and contains a fixed number of entries having a one-to-one correspondence to the cache lines of the cache to which it corresponds. The cache line state directory is used to determine whether it is necessary to send an invalidation message to the device cache. In the preferred embodiment, a dedicated portion of the cache line state directory structure corresponds to an I/O bridge device cache. Preferably, the cache line state directory also maintains state for one or more processor caches in a different format. The computer system preferably uses a NUMA architecture, the directories being maintained by node servers in each node.

Method and apparatus for tracking cached addresses for maintaining cache coherency in a computer system having multiple caches

An apparatus and method is disclosed for flushing a cache in a computing system. In a multinode computing system a cache in a first node may contain modified data in an address space of a second node. The cache in the first node must be purged prior to shutting down the first node. The computing system uses a random class replacement scheme for the cache. A cache flush routine sets a cache flush mode in a class replace select mechanism, overriding the random class replacement scheme. With the random class replacement scheme overridden, a minimum number of fetches will flush all the cache lines in the cache, each fetch loading the cache with a cache line not already in the cache. No additional delay penalty is incurred in a critical path through which fetches and stores to the cache must pass.

Method and apparatus to purge remote node cache lines to support hot node replace in a computing system

A memory cache sequencer circuit manages the operation of a memory cache and cache buffer so as to efficiently forward memory contents being delivered to the memory cache via the cache buffer, to a multithreading processor awaiting return of those memory contents. The sequencer circuit predicts the location of the memory contents that the processor is awaiting, and speculatively forwards memory contents from either the cache buffer or memory cache, while simultaneously verifying that the speculatively forwarded memory contents were correctly forwarded. If the memory contents were incorrectly forwarded, the sequencer circuit issues a signal to the processor receiving the speculatively forwarded memory contents to ignore the forwarded memory contents. This speculative forwarding process may be performed, for example, when a memory access request is received from the processor, or whenever memory contents are delivered to the cache buffer after a cache miss. The sequencer circuit includes a plurality of sequencers, each storing information for managing the return of data in response to one of the potentially multiple misses and resulting cache linefills which can be generated by the multiple threads being executed by the processor. For each thread, there is one designated sequencer, which is managing the most recent cache miss for that thread; the information stored by the designated sequencer is used to predict the location of data for speculative forwarding, subject to subsequent verification based on the information in other sequencers and the cache directory.

Accessing data from a multiple entry fully associative cache buffer in a multithread data processing system

The data processing system includes a plurality of execution units forming a plurality of processing pipelines. The plurality of processing pipelines process instructions and include a storage pipeline. The data processing system further includes an instruction unit and a storage control unit. The instruction unit outputs instructions to the plurality of execution units, and controls execution of multiple threads by the plurality of execution units. If an instruction for a first thread in the storage pipeline experiences a cache miss and the instruction unit decides to switch threads, the instruction unit begins processing a second thread. The instruction unit also issues a data request to the storage control unit to obtain the missing data. During processing of the second thread, unused slots will appear in the storage pipeline because it is not possible to always dispatch instructions to completely keep the pipelines filled. After the requested data returns from higher level memory, the storage control unit will dispatch the instruction from the first thread having received the cache miss to an unused slot in the storage pipeline. Consequently, this instruction from the first thread will be processed along with the instructions from the second thread.

Background completion of instruction and associated fetch request in a

A method and apparatus are provided for communicating translation command information in a multithreaded environment in a computer system. The computer system includes a processor unit, an instruction unit coupled to the processor unit, a cache coupled to the processor unit, a main memory, and a storage control unit including a dataflow control partition, a cache control partition, a translation control partition. A translation miss signal is sent from the dataflow control partition to the translation control partition, responsive to detecting a translation miss condition. A translation command next signal is sent from the translation control partition to the cache control partition responsive to the translation miss signal. Then a translation command signal is sent from the translation control partition to the cache control partition. Responsive to the translation miss signal, a steal command signal is applied to the instruction unit for providing the translation command priority over execution of another thread. A series of the translation command signals are sent from the translation control partition to the cache control partition, and in one control cycle, the translation control partition can receive a translation command taken signal from the cache control partition for a translation command signal and can receive a translation data valid signal from the cache control partition for another translation command signal.

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Rochester, MN, United States of America

Duane Arlyn Averill