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Burroughs' B Series Systems. E. A. Hauck B. A. Dent Presenter: Yi Ma and Hongliang Gao. The Objectives.
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Burroughs' B Series Systems E. A. Hauck B. A. Dent Presenter: Yi Ma and Hongliang Gao
The Objectives • The basic objective in designing the system was to define a complete system, both hardware and software together, to enable programs written in high level languages to be compiled and run efficiently. University of Central Florida
Main Features • Important features: • Dynamic storage allocation • Reentrant programming • Recursive procedure facilities • A tree structured stack organization • Memory protection • An efficient interrupt system University of Central Florida
Contents • The Objectives • Main Features • B6500/B7500 Processor • The Stack • Data Addressing • Non-local Addressing • Multiple Stacks and Re-Entrant Code • The Operating System • Summary University of Central Florida
B6500/B7500 Processor • Basic machine instruction: operator syllable • 8 bits to a maximum of 96 bits • Hardware implemented stack • Data word • 51 bits (3 bits tag + 48 bits data) • Tag: data/operator, memory protection University of Central Florida
IN/OUTPUT Path of data to stack Top of stack register A X B Y S Fast. Can hold two operands. If double precision, A+X & B+Y. WORD ntx Stack area assigned to program TOS WORD Stack limit register Stack area currently in use SL (Stack Limit) BOS (Base of Stack) WORDn Stack memory area The Stack University of Central Florida
Data Addressing • Three mechanisms: • Data Descriptor (DD)/ Segment Descriptor (SD), • Addresses which are located outside of the job's stack area. • Absolute machine address. • Indirect Reference Word (IRW), • Relative address • Address within the immediate environment of the job's stack • Stuffed Indirect Reference Word (IRWS). • Relative address • Beyond the immediate environment of the current procedure University of Central Florida
Non-Local Addressing • Facility for storing the dynamic history of a program under execution • Stack history list • Addressing environment list • Mark Stack Control Words (MSCW) University of Central Florida
MSCW DF MSCW DF MSCW DF Outer program block Procedure ‘C’ Procedure ‘D’ Procedure ‘A’ MSCW DF Non-Local Addressing The program{ A{ B{} B; } C{ real v4; D{ A; } D; } C; } TOS WORD S Procedure ‘B’ F Stack history list MSCW DF • Procedures are entering … • Procedure B exits. • Non-Local Addressing Problem University of Central Florida
Non-Local Addressing cont. • Address Couple: • The lexicographical level • The index University of Central Florida
Procedure ‘A’ Procedure ‘D’ Procedure ‘C’ Outer program block Non-Local Addressing cont. TOS WORD S Procedure ‘B’ F Stack history list Display registers MSCW DISP DF D31 MSCW DISP DF MSCW DISP DF D4 D3 D2 MSCW DISP DF D1 D0 MSCW DISP DF University of Central Florida
Multiple Stacks and Re-Entrant Code • Code sharing University of Central Florida
The Operating System • The operation of the system was to be directed by a Master Control Program (MCP) • Supports multiprogramming • 40 interrupt conditions (including timing interrupt) University of Central Florida
Summary • Hardware: • Multiple Stacks • Programming: • Be done in ALGOL and COBOL • Main features: • Dynamic storage allocation • Reentrant programming • Recursive procedure facilities • A tree structured stack organization • Memory protection • An efficient interrupt system University of Central Florida
References • “Burroughs’ B6500/B7500 Stack Mechanism”, E. A. Hauck and B. A. Dent, Chapter 16 of Computer Structures: Principles and Examples, McGraw-Hill, 1982 • “Operating System For The B 5000”, C. Oliphint, 1964 • “Studies In Operating Systems”, R. M. McKeag and R. Wilson, Academic Press, 1976 University of Central Florida
Thank you! Questions? University of Central Florida