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Dynamic Retrieval of Page Tables in a Two Level Dynamic Address Translation System

IP.com Disclosure Number: IPCOM000079849D
Original Publication Date: 1973-Sep-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Kern, RM: AUTHOR [+2]

Abstract

Some operating systems do not permit execution if both levels required for dynamic address translation are not present in real storage. If a segment translation exception occurs, it is handled as an error condition. This requires that the pages containing the tables be permanently resident in real storage, even when the tables are not currently in use.

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Dynamic Retrieval of Page Tables in a Two Level Dynamic Address Translation System

Some operating systems do not permit execution if both levels required for dynamic address translation are not present in real storage. If a segment translation exception occurs, it is handled as an error condition. This requires that the pages containing the tables be permanently resident in real storage, even when the tables are not currently in use.

The process is initiated by a hardware program interrupt with a segment translation exception condition. The logical address causing the condition is used as an index into a resident table, which indicates whether the page table required to translate the address exists. If the page table does not exist, an error is recognized. If the page table exists, the resident table provides a description of where the page table resides on external storage. This description is used to retrieve the page containing the page table. The resident table is searched for all other page tables contained in the retrieved page. The appropriate entries in the segment table for all page tables contained in the retrieved page are modified, to indicate where in real storage the retrieved page table resides and that it is available for use in translation. Normal system operation is then resumed.

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