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Storage Protect Key Array for a Multiprocessor System

IP.com Disclosure Number: IPCOM000074765D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Alvarez, JA: AUTHOR [+3]

Abstract

A storage protection technique is described for a multiprocessing system with a storage hierarchy, wherein selected blocks of data from main storage are stored in a local buffer for fast access by the CPU. A five-bit key is associated with each storage protect area in main memory. The key is used to establish the right of access to the storage protect area by comparing the key in the storage to a protection key. Storage protection must be afforded this data since it is simply a local copy of a portion of main storage.

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Storage Protect Key Array for a Multiprocessor System

A storage protection technique is described for a multiprocessing system with a storage hierarchy, wherein selected blocks of data from main storage are stored in a local buffer for fast access by the CPU. A five-bit key is associated with each storage protect area in main memory. The key is used to establish the right of access to the storage protect area by comparing the key in the storage to a protection key. Storage protection must be afforded this data since it is simply a local copy of a portion of main storage.

Protection of the data is provided by maintaining a copy of the keys from a selected number of the storage protect areas in a key array. A separate key array is associated with each local buffer in the multi-processing system.

When a block of data is fetched into the local buffer from main storage, the key associated with that block is entered into the key array.

The row of the key array into which the key is placed is defined by bits K1 through 20 of the address. Bits 8 through (K1-1) of the address are entered along with the key.

Each access of the local buffer is accompanied by the fetch of an entry from the key array. Bits K1 through 20 define the entry to be fetched. Bits 8 through K-1 of the address are compared to the address field contained in the key array. A match indicates that the key obtained is the key associated with the storage protect area identified by the address. A mismatch in...