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Fast Path for Fetching and Modifying Page Frame Table Entries Without Disrupting the Cache Contents

IP.com Disclosure Number: IPCOM000036339D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Thatcher, LE: AUTHOR [+2]

Abstract

In a store-in cache environment this disclosure solves the problem of writing storage without first bringing the data into the cache arrays.

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Fast Path for Fetching and Modifying Page Frame Table Entries Without Disrupting the Cache Contents

In a store-in cache environment this disclosure solves the problem of writing storage without first bringing the data into the cache arrays.

In processor implementations incorporating a store-in data cache, there exist a number of Load/Store functions which for performance reasons should not be brought into the data cache since they are accessed once and then not referenced again (e.g., Page Frame Table (PFT) updates of reference, change, or lockbits). The processor requires the capability to request cache reloads from storage, modify the data, and then store-back quickly without disrupting the cache contents. The following implementation provides a simple solution to the problem.

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A Cache Reload Buffer (CRB) is used to accumulate data from storage when a cache reload is being serviced. The processor has the unique ability to modify the contents of the CRB in the same way it can perform writes to the array itself. A Store-Back Buffer (SBB) is provided to accept the modified data from the array for store-back to memory at a later time, freeing up the contents of the array for newly fetched storage data to be loaded in.

By providing a direct path between the CRB and the SBB, data can be fetched from storage in the same fashion as a standard data cache reload, modified in the CRB, loaded into the SBB directly (without disrupting the cache contents), and...