Browse Prior Art Database

Direct Execution of Alien Read Only Architectures

IP.com Disclosure Number: IPCOM000080291D
Original Publication Date: 1973-Nov-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Larson, LE: AUTHOR

Abstract

Simulating (emulating) an Alien Read-Only Architecture (AROA) without the normal overhead involved in instruction fetch and validation is accomplished, because Read-Only Architectures maintain code execution strings unique from data strings and the code execution strings are not modified/altered during program execution. Where code strings are entered or deleted from the system, there is a formalized sequence of operations to be performed, i.e., LINKEDIT. These architectures prevent such things as reading a card and branching to a data field in the card.

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Direct Execution of Alien Read Only Architectures

Simulating (emulating) an Alien Read-Only Architecture (AROA) without the normal overhead involved in instruction fetch and validation is accomplished, because Read-Only Architectures maintain code execution strings unique from data strings and the code execution strings are not modified/altered during program execution. Where code strings are entered or deleted from the system, there is a formalized sequence of operations to be performed, i.e., LINKEDIT. These architectures prevent such things as reading a card and branching to a data field in the card.

The AROA is given an empty address space known as the Source Address Space (SAS) and a minimum size Execution Address Space (EAS) composed of three elements which are never deleted or overlayed; the simulation prologue (SP) which "opens" data files, the simulation epilogue (SE) which "closes" data files, and an exit to SE to catch errors is the source code. A fourth element is created which is changed when code strings are added/deleted from the system. This is the pointer table which contains the address of the source code string, and the address of its compiled counterpart. The structure of the SAS and EAS is shown in Fig. 1.

At each point in the AROA where a new code string can be added, the code string is put into the SAS as provided by the formal interface. Each instruction in the code string is fetched and a code string generated in the EAS to support the in...