Computer Hardware and Design

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Computer Hardware and Design
EE3A1

RISC MICROPROCESSOR

~2~ Table of Contents
I. II. III. IV. V. VI. VII. VIII. IX. Abstract .................................................................................................................................... 3 Introduction .......................................................................................................................... 3 Design of the Microprocessor .............................................................................................. 3 Challenges Faced and its solution ........................................................................................ 4 Results .................................................................................................................................. 5 Limitations ........................................................................................................................... 6 Conclusion ........................................................................................................................... 6 Appendix 1 ....................................................................................................................... 7 Appendix 2 ......................................................................................................................... 18

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I. Abstract Microprocessors consist of thousands of logic gates. By using the VHSIC hardware description language (VHDL), simulation and testing of the microprocessor is possible before manufacturing it. In this report a simple RISC microprocessor is made using VHDL. II. Introduction In this report the design of the microprocessor will be shown and the reasons why the microprocessor is designed will be explained. The problems faced and the solutions made to counter the problems will also be stated. The results of the calculations from the microprocessor will be shown. Lastly, the speed of the microprocessor will be calculated and its limitations will be explained.

III.

Design of the Microprocessor The microprocessor in this report is made up of a Machine Register, a File Register, an Arithmetic Logic Unit (ALU) and pipelines for both the Address 3 and Opcode. Pipeline Opcode Opcode

Address 1

Output 1

An explanation of what happens at each clock cycle will be explained below where each number represents the clock cycle in the microprocessor

Machine Register

ALU
Address 2

Output 2
Address 3

Pipeline Address 3
Input

File Register
Diagram 1. Structure of the microprocessor

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1. 32 Bit Instructions will be given from the compiler to the machine register at a rate that is set by the user. The instructions will be broken up into sections which consists of the 6 Bit Opcode, and 3 5 Bit Addresses. The signals would then be sent. 2. The Opcode will then enter the Pipeline Opcode, which is a register that helps to delay the signal so as to allow the values from the file register to be processed. The 2 signals moving in Address 1 and 2 will move into the File register and the values stored in the respective addresses will be pulled and sent to the ALU. The signal in address 3 will also enter a Pipeline to delay its arrival to the file register. 3. Output 1 and 2 will reach the ALU at the same time as the Opcode, enabling the ALU to calculate correctly. The signal in address 3 will reach the file register at this cycle. 4. The ALU would have calculated and sent the results to the input of the file register. The file register will perform a write back using the value of address 3 and the result from the ALU. This design was chosen as it eliminates data hazards that might occur by ensuring the correct address value and the correct opcode is read by placing in pipelines to stall the signals. Without the pipeline the values at Input would be corrupted. The instructions were also rearranged for efficiency.

IV.

Challenges Faced and its solution Before this design...
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