Chapter 05: Basic Processing Units … Control Unit Design Organization

Lesson 01: Basic Processing Units Basic Processing Units

Schaum’s Outline of Theory and Problems of Computer Architecture 2 Copyright © The McGraw-Hill Companies Inc. Indian Special Edition 2009 Processor Block Diagram

Execution Unit

Schaum’s Outline of Theory and Problems of Computer Architecture 3 Copyright © The McGraw-Hill Companies Inc. Indian Special Edition 2009 1. Execution Unit

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• Includes Arithmetic Logic Unit (ALU) • Contains the hardware that executes instructions • Includes the hardware that fetches and decodes instructions

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• Does actual computation using the arithmetic logic unit(s) [ALUs] • Contain separate execution units for integer and floating-point computations in certain processors • Hardware required to handle the two data types, integer and floating point • Modem processors often use multiple execution units to execute instructions in parallel to improve performance

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Schaum’s Outline of Theory and Problems of Computer Architecture 8 Copyright © The McGraw-Hill Companies Inc. Indian Special Edition 2009 Current program register set used by the program GPRs (General Purpose Registers • Program counter • Status register (PSW Processor Status Word) • Other processor registers used by a program instruction

Schaum’s Outline of Theory and Problems of Computer Architecture 9 Copyright © The McGraw-Hill Companies Inc. Indian Special Edition 2009 Register set used by the execution unit

• Instruction Register (IR) • Instruction Decoder (ID) • MAR and MDR Registers • Other processor registers used by a program instruction

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• Values stored in the register accessed more quickly than data stored in the memory • Support to simultaneous access of registers by the processor

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• Allows an operation, such as an addition, to read all of its inputs from the register file at the same time, rather than having to read them one at a time

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• Controls the rest of the processor, determining when instructions can be executed • Controls what sequences of operations are required to execute each instruction.

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• Very small fraction of the processor hardware compared to the ALUs and the register file

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• Complex control unit one of the more difficult parts of a processor to design

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Schaum’s Outline of Theory and Problems of Computer Architecture 17 Copyright © The McGraw-Hill Companies Inc. Indian Special Edition 2009 Summary

Schaum’s Outline of Theory and Problems of Computer Architecture 18 Copyright © The McGraw-Hill Companies Inc. Indian Special Edition 2009 We learnt

Processing units of a computer  • Processor Control unit, IR, ID, PSW, ALU, MAR, MDR, Registers • Address, data and control buses • Memory • Input-Output System  Hard Disk, CD- ROM, video card, ...

Schaum’s Outline of Theory and Problems of Computer Architecture 19 Copyright © The McGraw-Hill Companies Inc. Indian Special Edition 2009 We learnt

• Execution unit Includes the hardware that fetches and decodes instructions • Does actual computation using the arithmetic logic units (ALUs) • General Purpose registers • Program counter • Status register • other registers

Schaum’s Outline of Theory and Problems of Computer Architecture 20 Copyright © The McGraw-Hill Companies Inc. Indian Special Edition 2009 We learnt

• Complex control unit in a processor with multiple addressing modes and large opcodes

Schaum’s Outline of Theory and Problems of Computer Architecture 21 Copyright © The McGraw-Hill Companies Inc. Indian Special Edition 2009 End of Lesson 01 on Basic Processing Unit

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