Apple Inc.

Mahnaz P Sadoughi-Yarandi

Brian P Lilly

Hari Kannan

Perumal R Subramonium

Gerard Richard Williams

Prashant Jain

Pradeep Kanapathipillai

Perumal R Subramoniam

Helen Huang

Gerard R Williams Iii

Hari S Kannan

A mechanism for evicting a cache line from a cache memory includes first selecting for eviction a least recently used cache line of a group of invalid cache lines. If all cache lines are valid, selecting for eviction a least recently used cache line of a group of cache lines in which no cache line of the group of cache lines is also stored within a higher level cache memory such as the L1 cache, for example. Lastly, if all cache lines are valid and there are no non-inclusive cache lines, selecting for eviction the least recently used cache line stored in the cache memory.

Least recently used mechanism for cache line eviction from a cache memory

A method and apparatus for selectively powering down a portion of a cache memory includes determining a power down condition dependent upon a number of accesses to the cache memory. In response to the detection of the power down condition, selecting a group of cache ways included in the cache memory dependent upon a number of cache lines in each cache way that are also included in another cache memory. The method further includes locking and flushing the selected group of cache ways, and then activating a low power mode for the selected group of cache ways.

Selective cache way-group power down

A method and apparatus for evicting cache lines from a cache memory includes receiving a request from one of a plurality of processors. The cache memory is configured to store a plurality of cache lines, and a given cache line includes an identifier indicating a processor that performed a most recent access of the given cache line. The method further includes selecting a cache line for eviction from a group of least recently used cache lines, where each cache line of the group of least recently used cache lines occupy a priority position less that a predetermined value, and then evicting the selected cache line.

Methods for cache line eviction

Systems and methods for reducing leakage power in a L2 cache within a SoC. The L2 cache is partitioned into multiple banks, and each bank has its own separate power supply. An idle counter is maintained for each bank to count a number of cycles during which the bank has been inactive. The temperature and leaky factor of the SoC are used to select an operating point of the SoC. Based on the operating point, an idle counter threshold is set, with a high temperature and high leaky factor corresponding to a relatively low idle counter threshold, and with a low temperature and low leaky factor corresponding to a relatively high idle counter threshold. When a given idle counter exceeds the idle counter threshold, the voltage supplied to the corresponding bank is reduced to a voltage sufficient for retention of data but not for access.

L2 cache retention mode

Processors and methods for coordinating prefetch units at multiple cache levels. A single, unified training mechanism is utilized for training on streams generated by a processor core. Prefetch requests are sent from the core to lower level caches, and a packet is sent with each prefetch request. The packet identifies the stream ID of the prefetch request and includes relevant training information for the particular stream ID. The lower level caches generate prefetch requests based on the received training information.

Coordinated prefetching based on training in hierarchically cached processors

Processors and methods for preventing lower level prefetch units from stalling at page boundaries. An upper level prefetch unit closest to the processor core issues a preemptive request for a translation of the next page in a given prefetch stream. The upper level prefetch unit sends the translation to the lower level prefetch units prior to the lower level prefetch units reaching the end of the current page for the given prefetch stream. When the lower level prefetch units reach the boundary of the current page, instead of stopping, these prefetch units can continue to prefetch by jumping to the next physical page number provided in the translation.

Growing community of inventors

Santa Clara, CA, United States of America

Mahnaz P Sadoughi-Yarandi