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Space Identifier for Computer Systems With Extended Memory Addressing

IP.com Disclosure Number: IPCOM000061645D
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Kurtz, HL: AUTHOR [+3]

Abstract

A technique is described whereby a system logical address space is divided into 256 sub spaces. These sub spaces are uniquely divided by an eight-bit system identifier (SID). The SID is analogous to an address key, in that it is a "logical name" for an address space and is managed as part of the run time context of a program. Each of the 256 sub spaces, which make up the system address space, can be up to 16 megabytes in size. During execution, the active level has two SIDs residing in the Extended Level Status Block (ELSB) (see the preceding article for a description of the ELSB). The effective address generated by the processor can be in one of three formats as shown below, depending upon the address mode of the system, the addressing mode of the program executing and the state of the translator.

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Space Identifier for Computer Systems With Extended Memory Addressing

A technique is described whereby a system logical address space is divided into 256 sub spaces. These sub spaces are uniquely divided by an eight-bit system identifier (SID). The SID is analogous to an address key, in that it is a "logical name" for an address space and is managed as part of the run time context of a program. Each of the 256 sub spaces, which make up the system address space, can be up to 16 megabytes in size. During execution, the active level has two SIDs residing in the Extended Level Status Block (ELSB) (see the preceding article for a description of the ELSB). The effective address generated by the processor can be in one of three formats as shown below, depending upon the address mode of the system, the addressing mode of the program executing and the state of the translator. Format 1 - Extended Processor Status Word (EPSW) bit 09 on, Extended Level Status Register (ELSR) bit 20 on and Translator enabled.

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Bit 0 - This bit, when on, specifies that the User SID is active SID. When off, it specifies the System SID as the active SID. Bits 1-7 - Reserved, should be zero. Bits 8-20 - This 13-bit field specifies 1 of 8K logical segments within the address space specified by the selected SID. Bits 21-31 - This 11-bit field specifies 1 of 2K bytes within the selected segment. Format 2 - Extended Processor Status Word (EPSW) bit 09 on, ELSR bit 21 OFF and Translator...