Silicon Graphics, Incorporated

Joseph T Scanlon

Peter Y Hsu

Joseph P Bratt

William A Huffman

John Brennan

Man K Tang

Steve J Ciavaglia

Paul Kingsley Rodman

Chandra Shekhar Joshi

Monica R Nofal

John Brennen

Steven J Ciavaglia

Steve Ciavagia

A conflict resolution system for interleaved memories in processors capable of issuing multiple independent memory operations per cycle. The conflict resolution system includes an address bellow for temporarily storing memory requests, and cross-connect switches to variously route multiple parallel memory requests to multiple memory banks. A control logic block controls the address bellow and the cross-connect switches to reorder the sequence of memory requests to avoid conflicts. The reordering removes conflicts and increases the occurrence of alternating memory requests that can issue simultaneously.

Conflict resolution in interleaved memory systems with multiple parallel

A method for preventing deadlock due to the need for data exclusivity when performing forced atomic instructions in a multi-level cache in a multi-processor system. The system determines whether an aligned multi-byte word in which the data of a forced atomic instruction, such as an integer store operation, is exclusive in a first level cache. If so, the forced atomic instruction is allowed to enter a second level cache pipeline. If not, the forced atomic instruction is prevented from entering the second level cache pipeline and a cache miss and fill operation is initiated to cause the aligned word to be exclusive in the first level cache.

Method for preventing multi-level cache system deadlock in a

A method for preventing data loss and deadlock in a multi-processor computer system wherein at least one processor in the computer system includes a split-level cache. The split-level cache has a byte-writable first-level and a word-writable second level. The method monitors the second level cache to determine if a forced atomic (FA) instruction is in a second level cache pipeline. If an FA instruction is determined to be in the second level cache pipeline, then interventions to the second level cache are delayed until the FA instruction exits the second level cache pipeline. In this manner data written by operation of cache memory access instruction that cause the interventions is not destroyed by the execution of the FA instruction, thereby preventing data loss. The method also monitors the second level cache pipeline to determine if a possible miss (PM) instruction is in the second level cache pipeline. If a PM instruction is determined to be in the second level cache pipeline, the FA instructions are prevented from entering the second level cache pipeline such that execution of interventions to the second level cache is not prevented when an instruction in the second level cache may be detained to process an intervention in its behalf, thereby preventing deadlock between processing units of the computer system.

System and method for controlling split-level caches in a

A processor system that is switchable between a normal mode of operation without precise floating point exceptions and a debug mode of operation with precise floating point exceptions. The processor system includes a dispatch for dispatching integer and floating point instructions, an integer unit having a multi-stage integer pipeline for executing the integer instructions, and a floating point unit having a multi-stage floating point pipeline for executing the floating point instructions. The system begins operation in the normal mode, and upon receipt of an instruction to 'switch to debug mode,' the processor switches to the debug mode of operation with precise exceptions. In the debug mode, once a floating point instruction has been dispatched, all other instructions are prevented from being committed until the system determines whether the floating point instruction generates an exception. Thus, permitting the system to signal precise exceptions when not in the normal mode.

Debug mode for a superscalar RISC processor

A set associative translation lookaside buffer (TLB) that supports variable sized pages without requiring the use of a separate block TLB. The TLB includes a hashing circuit that creates an index into the TLB for a virtual address using different bits from the virtual address depending on the page size of the address, and a comparator that compares virtual address identifiers or portions of virtual address identifiers stored in the TLB to the current virtual address to determine if a translation to the current virtual address is stored in the TLB.

Variable page size translation lookaside buffer

A split level cache memory system for a data processor includes a single chip integer unit, an army processor such as a floating point unit, an external main memory and a split level cache. The split level cache includes an on-chip, fast local cache with low latency for use by the integer unit for loads and stores of integer and address data and an off-chip, pipelined global cache for storing arrays of data such as floating point data for use by the array processor and integer and address data for refilling the local cache. Coherence between the local cache and global cache is maintained by writing through to the global cache during integer stores. Local cache words are invalidated when data is written to the global cache during an army processor store.

Growing community of inventors

Sunnyvale, CA, United States of America

Joseph T Scanlon