Basic Von Neumann Designs

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1 COMP 273 Assignment #2 Part One Due: Monday October 12, 2009 at 23:55 on Web CT Mini-Project Due: Monday November 9, 2009 at 23:55 on Web CT Basic Von Neumann Designs This assignment is divided into two sections. The first section is due in two weeks and you must answer these questions on your own. The second section is a mini-project that you are to work on in a team of 2 or 3 students. The mini-project is due in 6 weeks. Everything must be submitted to Web CT. This assignment has two submission boxes. One box is for Part One, and is named Assignment 2. The other box is for the Mini-Project, and it is named Mini Project. Everyone must submit his or her own unique solution to the Part One assignment box. In the case of the mini-project, everyone in your team must submit the same submission files in his or her own Mini-Project assignment box. Make sure that you include a text file with the names of all your team members and their student ID numbers. This will help to speed up grading and make sure that everyone in your team receives the same grade. PART ONE (20 points) Please answer these questions on your own and submit your own unique solution to Web CT. QUESTION 1: (6 Points) In class we talked about flat and pipelined CPU control units. Pipelined CPUs improve the performance of the CPU as compared to classical CPUs. This is true as long as there are no faults. Derive two formulas: The first formula expresses the performance improvement experienced in a pipelined processor assuming no faults and all instructions are relatively similar. The second formula expresses the performance loss due to a single fault (keep in mind that this must take into account where and why the fault occurred you will need to express this as a probability). QUESTION 2: (5 Points) Given the classic CPU design as presented in class, write the sequence of micro-operations required to do the following: a) add an immediate operand with general purpose register #5 and store it into GP register #6 b) execute the instruction at the address stored in general purpose register #2 c) execute the instruction BEQ R1,R2,LABEL Where BEQ means Branch If Equal An example micro-operation is written as follows: MBR Memory(MAR) : MBR loaded from RAM indexed by MAR Y MBR : MBR copied into register Y Z 5 + (Y) : register Z = 5 + Memory(Y) Prof. Joseph Vybihal Page 1 of 6

2 QUESTION 3: (6 Points) The following table represents a portion of memory from a computer. Refer to this table for the following questions: Address Data What binary value does location 3 and 6 contain? 2. The binary values within each location can be interpreted in many ways. We have seen that binary values can represent unsigned numbers, 2 s complement signed numbers, floatingpoint numbers, and so forth. Interpret location 0 and 1 as 2 s complement numbers Interpret location 4 as an ASCII value Interpret location 5 as an unsigned value Interpret location 5 as an address In the Von Neumann model, the contents of memory can also be an instruction. What instruction and parameters is stored in location 0 given the following instruction format: LW DESTINATION SOURCE OFFSET 0001 XXX XXX XXXXXX QUESTION 4: (3 Points) Answer the following questions: Where DESTINATION and SOURCE are unsigned binary integer representing a register. OFFSET is a signed binary integer. The source register s contents is added to the offset to get the address in memory who s data will be put into the destination register. LW means load word. The X represents a single bit. A. If a machine cycle is 2 nanoseconds (i.e. 2, 10-9 seconds), how many machine cycles occur each second? B. If the computer requires on the average eight cycles to process each instruction, and the computer processes instructions one at a time from beginning to end, how many instructions can the computer process in 1 second? C. In many of today s microprocessors, to speed up execution, a pipeline is formed to execute the instructions in stages. If we have an 8-stage pipeline and we assume it takes 1 cycle to pass through each stage, how many instructions can our eight cycle per instruction computer execute in 1 second? Prof. Joseph Vybihal Page 2 of 6

3 MINI-PROJECT (10 points + 3 bonus points) Assemble a team of 2 or 3 students, 3 are preferable, who will work together to construct the solution to this mini-project. Everyone in your team must submit the same thing into his or her Mini-Project assignment box on Web CT. Make sure to include a text file identifying your team members by name and ID number. Include your own name and ID number in this list. The what-to-hand-in section details how this submission should be constructed. This mini-project is segmented into two parts: the basic question and the bonus question. All teams must do the basic question. The bonus question is available if you found the basic question too easy. You must construct your mini-project using LOGISIM. BASIC QUESTION Draw and implement the circuit diagram for a Classical CPU. Your CPU s must include the following micro architecture: Component 1: Four general purpose registers Component 2: An ALU that performs integer addition, subtraction and comparisons with zero Component 3: A 4-bit status status register overflow, underflow, negative, and zero Component 4: PC with increment circuit Component 5: IR with CU Component 6: A 4-way cache with four instruction guess storing 16 words Component 7: The 20 word RAM (this is external to the CPU) with MAR, MDR and R/W bit Component 8: A private bus that can be used for a fast 4-word download to the instruction cache Component 9: A clock, you can assume that the entire machines runs off of a single clock Your CPU will operate in the following way: 1. If no more instructions in cache then fast-download from RAM 4 words into the cache at PC 2. IR = Cache(PC) 3. CU(IR) causes the CPU to carry out the instruction 4. Go to step 1 Important! - Do not be wasteful. Optimize your design in such a way that you use the minimum number of bits and the least number of cycles. In order to make the drawings easier you may use black boxes in the following cases: Only after you have designed a full sample circuit in detail you can then use it as a black box. You also do not need to design an entire circuit if you can convince me that the rest of the circuit is identical to the part you just drew. You then can create a black box to represent the complete circuit. You can reuse black-boxed components in other areas of your diagram, as you did in your previous assignment, if-and-only-if you drew one black box in detail. Your CPU must have the following elements: 1. A word is equal to a byte 2. The CPU has a sequencer that controls the CPU and understands the following machine language instructions: 2.1. ADD ADD Rx, Ry (the result is stored in A-OUT) 2.2. STORE STR Rx, Address (the contents of Rx is put into RAM at Address) 2.3. LOAD LD Ry, Address (the contents at Address from RAM is put into Ry) 2.4. Branch if Zero BZ Rx, Address (if Rx is zero then go to Address) 2.5. COMP Rx Takes the value in Rx and makes it s 2 s complement, stored in A-OUT 2.6. SUB Rx, Ry A-OUT = Rx Ry, using 2 s complement addition Prof. Joseph Vybihal Page 3 of 6

4 2.7. STOP RETURN (mysteriously, the program stops running) You must supply your own binary definition for these instructions (i.e. its op-code, parameters, etc.) Rx and Ry can be: Any of the 4 general purpose, A-OUT or Status registers R0 and R1 can be used for indirect addressing but not R2 nor R3 3. The CPU Sequencer must be able to implement the above 5 instructions. 4. An ALU System, consisting of: 4.1. LEFT and RIGHT input registers 4.2. A-OUT resultant register 4.3. A 4-bit STATUS register 4.4. The ALU can only perform 8-bit signed integer addition and subtraction 4.5. Subtraction is performed by 2's complement addition 5. You do not need to concern yourself with how the first instruction got into the PC. You do not need to concern yourself with how information arrived in the RAM in the first place. Just assume that the PC is initialized to zero and RAM has a program with data already at address zero in the RAM. 6. Please provide a simple program written in your language that can fit in your memory and be executed by your CPU. We will execute that program when we test your design. The program must be at least 10 instructions long. Other than the items listed above, you are free to design your CPU in any way you like. Please provide a name for your CPU (something cool would be nice). Do not only hand in the LOGISIM design. Also submit a simple document that provides the following: A black box summary of your entire CPU. This should fit on a single printed page. It would be a high-level view of the entire CPU. You should provide an additional page of text describing how it functions. Then submit your LOGISIM CPU and any black box files (separate from this document). Your document should give some information about each LOGISIM file you uploaded, what it is and how it should be used. The very last page of your document should be your assembler-like program and a description of your assembler language. BONUS QUESTION Listed below are three possible upgrades to your CPU. Each upgrade is worth 1 bonus point. You do not need to answer this in any particular order. Select 1, 2 or all three features to implement. A calculator-like 4-digit digital display This display is connected to a special 8-bit display register named DOUT. Any value stored in that register is automatically displayed. The register s default value is zero, but once loaded it keeps the value until changed by the program. A new instruction is needed for this: DOUT Rx. This will move the contents of the general purpose register into the DOUT register. ON/OFF Switch Provide circuitry that combines the clock with an ON/OFF switch for the computer. When the switch is on and the clock ticks the PC is set to zero and the computer starts executing the program in memory. How the program got there, we don t know. But you must initialize the PC to zero. Implement an additional computer instruction: HALT. This command turns off the computer. Multiplication Upgrade the ALU so that it can multiply! There is an easy way and a hard way to do this Provide an additional instruction: MULT Rx, Ry. The result it stored in A-OUT. Having so many instruction will require you to be very clever in your instruction formats. Prof. Joseph Vybihal Page 4 of 6

5 WHAT TO HAND IN Everything should be handed in electronically on Web CT. For PART ONE, each student is to submit his or her own unique solution to these questions on Web CT. Please submit this as a WORD, PDF or JPG file. Please submit this in the box called Assignment #2. You have two weeks to answer these questions. For the MINI PROJECT, students must work in teams of 2 or 3 people. They are all to hand in the same thing to Web CT. In addition to his or her solution, please also submit a text file identifying each team member by name and student ID number (each team member does this). Each person in the team will receive the same grade. This list will help us during grading. Submit your document as a WORD, EXCEL, PDF or JPG file. Submit your design as LOGISIM file(s). We will execute these files to confirm that your design runs. Copied files will lose all grades. Make sure to submit this in the box called MINI-PROJECT. You have 6 weeks to complete this mini-project. Name your CPU. Mini-Project Document This is a project submission and therefore must be presentable and professional in its looks. I require the following elements: 1. A cover page 1.1. Project title 1.2. Name of each team member with ID number 2. Table of contents 3. Section 1: Overview of CPU 3.1. High level diagram of the entire CPU in one picture 3.2. Overview of its functionality and flow 4. Section 2: LOGISIM File Breakdown 4.1. Using a top-down approach, describe each part of the CPU 5. Section 3: The Assembly Language 5.1. Define your instructions in assembly 5.2. Define your instruction bit formatting 5.3. Describe how you instructions execute over the CPU 5.4. Provide a sample program 6. Section 4: Appendix (optional) 6.1. The place for miscellaneous other things Prof. Joseph Vybihal Page 5 of 6

6 HOW IT WILL BE GRADED This assignment is worth 20 points, the mini-project is worth 15 points plus 3 bonus points. PART ONE is worth 20 points, graded proportionally Question 1: 6 point Question 2: 5 points Question 3: 6 points Question 4: 3 points PART TWO the Mini-Project is worth 15 points + 3 bonus points. Graded proportionally Design 10 points Running program 5 points Bonus points (3 in total) for mini-project 1 point for each bonus implemented correctly, 0 points otherwise. The entire bonus part (bonus question 1, or 2, or 3) must be implemented and working correctly to receive your bonus point. Prof. Joseph Vybihal Page 6 of 6

Midterm Examination - Answers October 25, 2012 In Class Instructor: Joseph Vybihal

McGill University School of Computer Science Introduction to Computer Systems Midterm Examination - Answers October 25, 2012 In Class Instructor: Joseph Vybihal Student Name: Student ID: Instructions No