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Inside and Outside Protection Keys with Dynamic Relocation

IP.com Disclosure Number: IPCOM000090679D
Original Publication Date: 1969-Jun-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Cohn, L: AUTHOR [+3]

Abstract

Word registers 1...6 hold required memory protect information for a computer task. The keys, limits, and relocation constants can be assigned by a computer monitor program. Memory locations in a computer can be protected against improper storing or improper storing and fetching. The protection is achieved by associating a storage key with one or more blocks of memory words and by comparing this key with a protection key accompanying the request for storage access.

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Inside and Outside Protection Keys with Dynamic Relocation

Word registers 1...6 hold required memory protect information for a computer task. The keys, limits, and relocation constants can be assigned by a computer monitor program. Memory locations in a computer can be protected against improper storing or improper storing and fetching. The protection is achieved by associating a storage key with one or more blocks of memory words and by comparing this key with a protection key accompanying the request for storage access.

A choice between using the inside key I or the outside key 0 is determined by whether the access request is to a location respectively within or outside a region as designated by a set of upper and lower address limits. The detection of a mismatch causes the access to be suppressed and a protection exception to be recognized. An inside key and an outside key can be associated with each CPU and I/O operation. When the upper limit is smaller than the lower limit, the protection-relocation feature degenerates to a single choice protection key feature for all memory locations, with the outside key always being the chosen protection key.

All addresses, used to refer to protected storage, are compared to the lower and upper limits of a region. The result of the comparison determines the choice between the inside or outside protection keys. If the reference is within the region, the inside key is used. Otherwise, the outside key controls access to the requested storage location.

Additionally, accesses to locations within the region are relocated by adding the relocation constant to the address. Relocation permits a CPU program and its data to be moved...