International Business Machines Corporation

Stephen William Mahin

Wilbur David Pricer

Paul David Kartschoke

Stephen J Ciavaglia

Stephen Michael Conor

Stephen Emery Rich

Lyman Henry Moulton, Iii

Sebastian Theodore Ventrone

Kenneth Joseph Goodnow

Alvar Antonio Dean

Paul T Gutwin

John W Goetz

Marc Raymond Faucher

Jay Gerald Heaslip

James Henry Hesson

Miles G Canada

Dana J Thygesen

John Wallace Goetz

Daniel Mathew Wronski

John Michael Keaty

Walter Esling

Pamela A Wilcox

Kevin William McCullen

The present invention provides a performance based system and method for dynamic allocation of a unified multiport cache. A multiport cache system is disclosed that allows multiple single-cycle look ups through a multiport tag and multiple single-cycle cache accesses from a multiport cache. Therefore, multiple processes, which could be processors, tasks, or threads can access the cache during any cycle. Moreover, the ways of the cache can be allocated to the different processes and then dynamically reallocated based on performance. Most preferably, a relational cache miss percentage is used to reallocate the ways, but other metrics may also be used.

Performance based system and method for dynamic allocation of a unified multiport cache

A method and apparatus are provided for managing cache allocation for a plurality of data types in a unified cache having dynamically allocable lines for first type data and for second type data. Cache allocation is managed by counting misses to first type data and misses to second type data in the unified cache, and by determining when a difference between a number of first type data misses and a number of second type data misses crosses a preselected threshold. A replacement algorithm of the unified cache then is adjusted in response to the detected crossing of the preselected threshold, the adjusting step including increasing a replacement priority of the first type data lines in the cache. The replacement algorithm preferably is an LRU algorithm wherein the adjusting step includes incrementing an age indication of the first type data lines. Hardware for implementing the inventive cache allocation management method comprises a miss counter configured to increment its count in response to a miss to first type data signal on a first counter input and to output a first logic state on a first counter output when the counter's count exceeds a first predetermined count. A priority adjustment circuit coupled to the first counter output increases the replacement priority of the first type data relative to the replacement priority of the second type data in response to the first logic state output by the miss counter.

Method and apparatus for allocating data and instructions within a shared cache

A processor system is provided that comprises a plurality of L0 caches, a processor having a plurality of execution units, and an L1 cache for caching any data and instructions used by the processor. A portion of the execution units provided are configured so that each execution unit within the portion accesses one of the L0 caches. Each of the L0 caches is accessible by only one of the portion of the execution units, and each L0 cache caches a subset of any data used by the processor which is not cacheable by any of the other L0 caches. The processor system preferably comprises an instruction dispatcher that dispatches instructions executable by the processor and that selectively designates data as cacheable by only one of the L0 caches, preferably at dispatch time.

Method and apparatus for improving caching within a processor system

A computer system supports control transfers between two architectures with different address ranges and/or different methods of calling programs which involve passing parameters, stack pointers and return addresses. Control is transferred between the architectures through a control transfer mode bit.

Computer system supporting control transfers between two architectures

An apparatus for use with a computer system for identifying dependencies within a register, which dependencies are established by a succession of instructions for the computer system. The register includes a plurality of cells which may be in a hierarchical arrangement of register storage sets. In its preferred embodiment, the apparatus comprises a storage means for storing a bit map, which bit map is configured to provide bit map identifications identifying designated register storage sets. The bit map represents the hierarchical arrangement. The apparatus further comprises a logic means for logically treating information, which logic means is coupled with the storage means and with the computer system. The logic means receives a first bit map identification from a first instruction (the first bit map identification identifies a first register storage set), and receives a second bit map identification from a second instruction (the second bit map identification identifies a second register storage set. The second instruction is subsequent in the succession to the first instruction. The first register storage set is a first storage locus for storing a target operand of the first instruction; the second register storage set is a second storage locus for storing a source operand for the second instruction. The logical treating effects the identifying of dependencies between the target operand and the source operand.

Method and apparatus for identifying dependencies within a register

A computer processor architecture which employs an on-chip cache macro and an on-chip memory map is described. The memory map contains indicia of the cachability of different segments of off-chip memory, preferably along with an indication of the read/write status of each off-chip memory segment. A processor generated address signal is then compared on-chip with the memory map to ascertain whether the generated signal falls within a segment which is cachable or uncachable and which is read-only or read/write.

On-chip memory map for processor cache macro

A mechanism which manages variable length instructions in cache is comprised of three cooperating elements designed to optimize self modifying code and anticipate next instructions for branch operand management. A content addressable memory (CAM) stores addresses of lines which have been accessed for instruction fetching. In a system having modifiable instruction stream (i.e., store to instruction stream), when the CAM matches, the system must retire certain instructions, flush instructions and then fetch the modified instruction stream. Boundary identification logic examines a field in each cache byte to determine the nature of the byte. This field is initially cleared at the time the cache line is loaded and filled with the line is fetched. An anticipation buffer designed to minimize the circuitry necessary for fetches across cache lines is loaded with sequentially anticipated prefetched instructions from the cache. These anticipated instructions can then be concatenated by a fetch aligner.

Superscaler instruction pipeline having boundary identification logic

Superscaler instruction pipeline having boundary indentification logic

Superscalar instruction pipeline using alignment logic responsive to

Growing community of inventors

Underhill, VT, United States of America

Stephen William Mahin