Question 1: What criteria define Von Neumann architecture? Identify clearly and coherently. Solution

Size: px

Start display at page:

Download "Question 1: What criteria define Von Neumann architecture? Identify clearly and coherently. Solution"

Gerard Tyler
5 years ago
Views:

1 This webpage has designed and created to represent the solutions of course assignment-2 of ITEC 1000: Introduction to Information Technologies. Little Man Computer model is originally developed by Dr. Stuart Madnick in The model demonstrates how different components of a computer works to complete an instruction. This assignment is prepared to solve total seven problems. Each problem is related with Little Man Computer Model as well as recent development of computer technology. Over the last 50 years computer technology is changed in-terms of capacity and speed but the basic model remains almost same. Question 1: What criteria define Von Neumann architecture? Identify clearly and coherently. John von Neumann the famous computer scientist joined as a consultant of ENIC or Electronic Numerical Integrator and Computer project at the University of Pennsylvania in With a very limited capacity on that period, ENIC had very limited memory in 20 locations each could contain a 10-digit decimal number. Another one hundred numbers could be store on read only memory. Programs were stored externally with heard wired device called Patch Panel. It needed many hours to change the program and Patch Panel had to rewiring Von proposed an improvement of the ENIC architecture. The most important change in the ENIC design was i. The concept of storage area where both program and data can be a stored internally. It solved the problem retrieve program using patch panel of ENIC machine and saved hundreds of hours of rewiring the Patch Panel. ii. ENIC machine was based on 10-digit decimal number. Von Neumann architecture proposed a binary system to process data. This concept allows the similarity of ON/OFF switches and Boolean logic. The Little Man Computer is an example of using Von Neumann architecture as a model of computer design. Little Man Computer Introduces the concept of memory, data store location and data operation. In deed invention of Von Neumann Architecture in 1945 is still the basic rule of modern computer technology. By this time capacity of storage, memory and processing speed became faster and faster but design remain almost same. Thus, Von Neumann is considered as the icon of computer revolution. Criteria that defines Von Neumann architecture is as follows: 1. Memory holds both programs and data known as Stored Program Concept which allows programs to be changed easily. 2. There is a single sequential numeric address for each and every memory location and so Memory is addressed linearly. 3. Memory is addressed by the location number without regard to the data contained within - Memory is always addressed by its sequential numeric address despite what data it contains.

2 Question 2: The following Little Man program is supposed to add two number inputs, subtract a third input number from the sum, and out put the result. (a) What is wrong with this program? A program is written in wrong format compare to what a user wants to perform. These current instructions are instructing Little Man to subtract addition of IN1 and IN2 from IN3 whereas user wants Little Man to subtract IN3 from addition of IN1 and IN2. (b) Repair the program so that it produces the correct results. OUT = IN1 + IN2 - IN3 mailbox mnemonic code Numeric code 00 IN STO IN ADD STO IN SUB OUT COB 000 OUT = IN1 + IN2 - IN3 mailbox mnemonic code Numeric code 00 IN STO IN ADD STO IN STO LDA SUB OUT COB 000

3 Question 3: A modern computer has a 32-bit memory address register. How much memory (in gigabyte) can this computer address? Show your work. Memory Address Registrar (MAR) determines the addressable memory capacity of a computer. For example in the Little Man Computer a two digit addresses results in total one hundred mailboxes or memory. Thus for MAR with width k bits allows total Memory Address M = 2 k 2 36 = 68,719,476, bit allows 68,719,476,736 In Gigabytes: 1kilobyte = 1024 bytes 68,719,476,736 / (1024 x 1024 x 1024) = 68,719,476,736 / 1,073,741,824 = 64 gigabytes A 36-bit MAR computer can address 64 gigabytes of memory. Question 4: Why are there two different registers (MAR and MDR) associate with memory? What are the equivalents in the Little Man Computer? Explain clearly and coherently. Memory address register (MAR) is associated with memory because it holds the addresses/locations from where instructions are to be read or written to. However, on ther other hand, MDR contains data to be stored in a memory. When reading from memory action occurs, data is addressed by MAR which is moved and stored into MDR and later used by central processing unit, CPU. However, when writing to memory required, the process it opposite. The CPU writes data to MDR to the memory location and its address is stored in MAR. Equivalents of MAR and MDR in the Little Man Computer is Instruction Location Counter and Mailboxes respectively. Question 5: If you were building a computer in out space, would you be likely to use some form of flash memory or RAM as main memory? Explain clearly and coherently?

4 An outer space computer will be benefited from use of a Flash memory. A flash memory is a non-volatile memory and therefore, it will retain its programs, data and values in a memory. A non-volatile RAM such as Flash memory allows restarting a computer without rebooting it. Flash memory is unsuitable to be used as a primary memory because it takes much more time to rewrite than standard RAM but it is critical in outer space to conserve energy and it takes significant amount of power and time with volatile RAM computer to return to its previous state. Question 6: As computer words get larger and larger, there is a law of diminishing returns: the speed of execution of real application program does not increase and may, in fact, decrease. Why do you suppose that this is so? As words get larger, there are more instructions to be executed and there takes more time to fetch an instruction execute them which decreases the performance of a computer overall. The speed of execution of an application program depends on how the computer word is optimized to retrieve or to store in a single operation. This process is determined by the size of the MDR and the width of bus that connects the memory with CPU. For a 8 bit instruction word 3 bits are used to define op code and rest 5 bits remains for memory address. Five bits allow total 2 5 =32 different addresses. Thus longer word like 16 bits, 24 bits or 32 bits even more can be used. With a 32 bits word 8 bits are used for op code and rest 24 bits are used for memory addresses. As the size of word increases the MDR needs enough room to fit in a single fetch. Computer memories are designed to allow to load or storage eight successive bytes in a single operation. So getting larger and larger words does not necessarily speed up the execution of application unless the memory data can be retrieved all at once from several successive addresses. Thus, increasing the size of word larger to larger all under the economic law of diminishing returns i.e. at some point adding more of a factor may decrease the total production. Question 7: How does the LM execute the CPU fetch-execute cycle of a store instruction below? A PC MAR Transfer the address from Program Counter to Memory Address Register B MDR IR Transfer the instruction from Memory Data Little Man read the location counter for example he reads the number 02. He walks to the mail box #02 Little man read a slip of paper inside the mail box #02. The Slip is a three digit number say 389. He

5 C IR[address] MAR Register to Instruction Register Address portion of the instruction loaded in MAR reads the first digit as the Store instruction and the last two digits as the Mail box Number where to be stored. Little man walks to the calculator; he reads a number in the calculator screen say 223. Little Man reads the address portion of the number 23 for which will be a new mail box#23. D A MDR* Accumulator copies data into MDR E PC + 1 PC Program counter increment. He writes the number 223 in a slip of paper and drops it in the mail box #89. He finished the current instruction and finally he walks to the location counter. He clicks the counter machine to fetch next instruction.

The CPU and Memory. How does a computer work? How does a computer interact with data? How are instructions performed? Recall schematic diagram:

The CPU and Memory. How does a computer work? How does a computer interact with data? How are instructions performed? Recall schematic diagram: The CPU and Memory How does a computer work? How does a computer interact with data? How are instructions performed? Recall schematic diagram: 1 Registers A register is a permanent storage location within