Advanced fine-grained cache power management

摘要

Methods and apparatuses for reducing leakage power in a system cache within a memory controller. The system cache is divided into multiple sections, and each section is supplied with power from one of two supply voltages. When a section is not being accessed, the voltage supplied to the section is reduced to a voltage sufficient for retention of data but not for access. The cache utilizes a maximum allowed active section policy to limit the number of sections that are active at any given time to reduce leakage power. Each section includes a corresponding idle timer and break-even timer. The idle timer keeps track of how long the section has been idle and the break-even timer is used to periodically wake the section up from retention mode to check if there is a pending request that targets the section.

主权项

1. A cache comprising:
a cache memory comprising a plurality of sections, wherein each section of the plurality of sections has a separately controllable power supply, wherein each power supply is configured to provide at least a first voltage and a second voltage, wherein the first voltage is sufficient for a section to retain its stored data, wherein the second voltage is sufficient for a request to access the section, and wherein the second voltage is higher than the first voltage; and a cache control unit, wherein the cache control unit is configured to:
limit a number of sections supplied with the second voltage to be less than or equal to a first threshold;for each section, utilize a corresponding idle timer to count a number of consecutive clock cycles during which the section is supplied with the second voltage and is not accessed by any requests; andcause a section to be supplied with the first voltage when an idle timer corresponding to the section expires.