Presented by

Ayan Ganguly Roll-MT/CS/45053/11

Sajal Mitra Roll-MT/CS/45072/11

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Symbolic Processor

• Computer purpose-built to run symbol-manipulation programs rather than programs involving a great deal of numerical computation.

• They exist principally for the

Artificial intelligence language LISPSome have also been built to run PROLOG.

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Symbol Processing Computers 

• Symbolics manufactures high-performance symbol processing computers and associated software.

• Symbol processing (or symbolic processing) includes computation with symbols, relationships, and graphical objects as well as numbers, characters & bits.

• By making complex problems easier to represent, symbol processing languages enhance programmer’s productivity.

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Symbol Processing Computers contd. 

• The Symbolics 3600 family is a line of 36-bit single-user computers designed for high-productivity software development and for the execution of large symbolic programs.

• 3600-family processors give the user all the computational power associated with multi-user timesharing computers in a dedicated workstation.

• This is accomplished via a new and unique machine architecture that supports high-speed symbol processing operations directly in hardware.

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Symbol Processing Computers contd. 

• The Symbolics-Lisp system software constitutes a large-scale programming environment, with over a half-million lines of system code accessible to the user.

• All of the system software is written in Symbolics-Lisp.

• A high-performance implementation of Symbolics Prolog is also available, as are compilers for more conventional languages. 

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Symbol Processing Computers contd.

 Some Typical Applications• Artificial Intelligence (AI).• Software Development.• Computer-aided Design (CAD).• Expert Systems.• Database and knowledge base servers.• Automated diagnostics . • Mathematics and physics research.• Industrial automation. • Image-making.• Animation for film and video.• Very-Large-Scale-Integration (VLSI) circuit design.• Communications and network control.• Speech recognition and understanding

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Symbol Processing Computers contd. 

In the previous applications some features are different than in numerical computing. Those are – Data & knowledge representations– Primitive operations– Algorithmic behavior– Memory– I/O & communications– Special architectural features.

Symbolic processor are also identified as – Prolog processors– Lisp processors– Symbolic manipulators.

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Characteristics of Symbolic Processors

• Knowledge representation

• Common operations

• Memory requirements

• Communications patterns

• Properties of algorithm

• Input/Output requirements

• Architecture features

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History of Symbolic Computing 

The economics of computer hardware and the computational demands made by modern software have converged to make personal, networked computers more attractive than timeshared systems.

Foreseeing this changing situation, researchers at the M.I.T. Artificial Intelligence Laboratory initiated the Lisp Machine project in 1974.

The project was aimed at developing a state-of-the-art personal computer that would support programmers developing large and complex symbolic programs. An important decision was made early in the design process: for consistency throughout the software environment, all of the system code would be written in a single language - Lisp.

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The Evolution of Symbolics, Inc. 

• In 1980, Symbolics, Inc., was formed to develop a line of symbol processing computer systems & related products.

• The most powerful & cot effective computer architecture developed by them is known as 3600 which replaced the microcode emulator architecture with special hardware to support high speed symbolic & numeric computations & to expand virtual memory to 1-GB.

• To correspond to the new hardware, the software development team made major enhancements to the software system.

• All system software for Symbolics computers is written in a dialect of the Lisp language called Symbolics-Lisp.

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LISP

Lisp is a computer programming language that originated as a tool for Artificial Intelligence (AI) research. AI is a branch of computer science that seeks to understand and model intelligent behavior with the aid of computers. Lisp is designed to symbolically represent objects in the world and the relationships that exist among them.

"Lisp" stands for "List Processing Language" as it was dubbed by Professor John McCarthy of M.I.T. (now at Stanford University).

At this time, most major artificial intelligence systems are written in Lisp.

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Hardware Overview 

This section outlines the features of the Symbolics 3600-family processor architecture .

• Dedicated 36-bit processor (32 bits data, 4 bits tag) with run-time data-type checking, providing full 32-bit integers and IEEE-compatible floating-point formats.

• 44-bit memory words with automatic detection of double-bit errors and both detection and correction of single-bit errors.

• A 1.024 GB demand-paged virtual memory with packaging for more than 30 Mbytes of semiconductor memory.

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Hardware Overview contd.

• MC68000-based front-end processor (FEP).

• Four serial input/output lines (both high- and low-speed), including one on the console .

• Generic Bus Interface with UNIBUS and MULTIBUS interfaces.

• Console processor based on dedicated microprocessor for handling keyboard and mouse input

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The 3600-family Processor 

• 36-bit internal data paths (32 bits data, 4 bits tag) with full 32-bit integers.

• Tagged architecture: run-time data-type checking with no overhead.

• Stack-oriented architecture, with large stack buffers (the top of the stack is always kept in a special high-speed memory) and caches for virtual memory and garbage collection operations.

• Stack pointers in hardware.

• Execution of most simple Lisp instructions in one machine cycle (180 to 250 nanoseconds variable), rather than the two or three cycle instructions of other Lisp Machines.

• IEEE-standard floating-point operations.

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The 3600-family Processor 

• Concurrent operations in hardware for high speed:

(i) Run-time data type checking.

(ii) Instruction fetch.

(iii) Instruction decode.

(iv) Instruction execution.

(v) Result data type checking.

(vi) Garbage collection support.

• Floating Point Accelerator option (greatly increases the speed of floating point numerical operations).

• Enhanced Performance Option (provides instruction prefetch unit, 2K instruction cache, and additional microcode).

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The Architecture of Symbolic 3600 Lisp Processor

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References

Books• Kai Hwang, Advance Computer Architecture, First edition,

Tata McGraw-Hill, 2001.

URLs• http://smbx.org/index.php/index.php?

option=com_content&task=view&id=18&Itemid=76• http://ed-thelen.org/comp-hist/vs-symbolics-3600.html• http://www.csbdu.in/virtual/DIGITAL%20MUP/5.3.php• http://www.h4ck3r.net/2010/06/14/some-opcode-design/• http://www.vycorporation.com/processing.htm

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