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Method for bit-power state information in data caches

IP.com Disclosure Number: IPCOM000033804D
Publication Date: 2004-Dec-28
Document File: 2 page(s) / 32K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for bit-power state information in data caches. Benefits include improved functionality, improved power efficiency, and improved performance.

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Method for bit-power state information in data caches

 

Disclosed is a method for bit-power state information in data caches. Benefits include improved functionality, improved power efficiency, and improved performance.

Background

              Conventional designs send data across buses without special encoding, which uses excessive power.

General description

              The disclosed method is bit-power state information in data caches. The method applies to on-chip memory that is burst-oriented. One or more additional bits stored in cache are used to encode data to save power.

Advantages

              The disclosed method provides advantages, including:

•             Improved power efficiency due to reducing the overall activity factor for bits on the bus

•             Improved power efficiency due to transferring full cache lines (not smaller pieces)

•             Improved performance due to minimizing latency

Detailed description

              The disclosed method stores extra bits in a data cache to reduce the amount of power used to transfer cache lines. For example, assume cache lines are 16 bits and buses are 4 bits wide. A cache line transfer takes four clocks. Sample data from a cache line transfer, distributed across the four clocks, can be:

•             1001

•             1100

•             0011

•             1110

              Power for the transfer is proportional to the activity factor of the bits. The activity factor on bit 0 of the bus, for example, is 100% because it toggles every clock. The outer caches (L1 and L2) may be low-power/low-leakage and may transfer cache lines (not smaller pieces), so line transfer power uses most of their active power. All of the solid lines show buses over which line traff...