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Move Character Instruction and Procedure to Avoid Crossing Page Boundary and Fast Circuit for Checking Address Range

IP.com Disclosure Number: IPCOM000049778D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Leiner, KL: AUTHOR

Abstract

This article describes a new set of Move Character instructions in which each instruction specifies in its op code the number of bytes to be moved. The instruction also contains the starting address of the move from and move to locations in storage. Using the instructions and beginning a move to on a corresponding byte length boundary assures that the move operation does not extend into the next page. A simple circuit checks that the move to address is on the boundary that corresponds to the byte length specified by the op code.

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Move Character Instruction and Procedure to Avoid Crossing Page Boundary and Fast Circuit for Checking Address Range

This article describes a new set of Move Character instructions in which each instruction specifies in its op code the number of bytes to be moved. The instruction also contains the starting address of the move from and move to locations in storage. Using the instructions and beginning a move to on a corresponding byte length boundary assures that the move operation does not extend into the next page. A simple circuit checks that the move to address is on the boundary that corresponds to the byte length specified by the op code.

Main store can be organized to hold units of data called pages in which each have a predetermined binary number of bytes, such as 1024, and each begin on a page boundary. A page boundary is a page starting address that has a fixed number of low order zeros that is the same number for each page. It is important to prevent a user of a page from storing across a page boundary and into a next page assigned to a different user. A Move Character instruction ordinarily specifies the beginning move to address and a byte count that may be long enough to extend across a page boundary. For a non-privileged user, the storage protect mechanism prevents this undesirable result. However, control programs usually operate without storage protect, and conventionally a check is made on the move to address and the byte count to prevent storing...