Understanding the Functional Units and Organization of a Computer, Summaries of Computer Architecture and Organization

Download Understanding the Functional Units and Organization of a Computer and more Summaries Computer Architecture and Organization in PDF only on Docsity! Introduction to Computer Organisation and Architecture Architecture and Organisation i Architecture is those attributes visible to the programmer 0 Instruction set, number of bits used for data representation, I/O mechanisms, addressing techniques. 0 e.g. Is there a multiply instruction? U Organization is how features are implemented 0 Control signals, interfaces, memory technology. 0 e.g. Is there a hardware multiply unit or is it done by repeated addition? Function 0 The following are the functions of the computer: 0 Data processing 0 Data storage 0 Data movement 0 Control Functional eau | (source and destination of data) view Operations (1) Data movement Operation (4) Processing from storage to I/O Structure - Top Level Computer Central Processing Unit Systems Interconnection | mmunication PS Structure - The CPU Internal CPU Interconnection Arithmetic and Login Unit Py Functional units of a computer Input unit accepts Arithmetic and logic unit(ALU): information: ‘Performs the desired y ‘Human operators, operations on the input *Electromechanical devices information as determined ‘Other computers by instructions in the memory Input omer Arithmetic npu . P Instr1 & Logic Instr2 Instr3 Datal Outpu Data2 Contro t l VO Stores Processor Output unit sends information: Control unit coordinates results of processing: ‘Instructions, various actions P 9: “Input, To a monitor display, ‘Data *To a printer *Out put Processing Information in a computer -- Instructions 0 Instructions specify commands to: 0 Transfer information within a computer (e.g., from memory to ALU) 0 Transfer of information between the computer and I/O devices (e.g., from keyboard to computer, or computer to printer) 0 Perform arithmetic and logic operations (e.g., Add two numbers, Perform a logical AND). i A sequence of instructions to perform a task is called a program, which is stored in the memory. 0 Processor fetches instructions that make up a program from the memory and performs the operations stated in those instructions. 0 What do the instructions operate upon? Information in a computer -- Data ) Data are the “operands” upon which instructions operate. Data could be: o Numbers, 0 Encoded characters. Data, in a broad sense means any digital information. Computers use data that is encoded as a string of binary digits called bits. Memory unit (contd..) 0 Processor reads/writes to/from memory based on the memory address: Access any word location in a short and fixed amount of time based on the address. Random Access Memory (RAM) provides fixed access time independent of the location of the word. Access time is known as “Memory Access Time”. ) Memory and processor have to “communicate” with each other in order to read/write information. 0 In order to reduce “communication time”, a small amount of RAM (known as Cache) is tightly coupled with the processor. 0 Modern computers have three to four levels of RAM units with different speeds and sizes: 0 Fastest, smallest known as Cache 0 Slowest, largest known as Main memory. Memory unit (contd..) 0 Primary storage of the computer consists of RAM units. 0 Fastest, smallest unit is Cache. 0 Slowest, largest unit is Main Memory. i Primary storage is insufficient to store large amounts of data and programs. 0 Primary storage can be added, but it is expensive. 0 Store large amounts of data on secondary storage devices: 0 Magnetic disks and tapes, 0 Optical disks (CD-ROMS). 0 Access to the data stored in secondary storage in slower, but take advantage of the fact that some information may be accessed infrequently. 0 Cost of amemory unit depends on its access time, lesser access time implies higher cost. Arithmetic and logic unit (ALU) () Operations are executed in the Arithmetic and Logic Unit (ALU). i Arithmetic operations such as addition, subtraction. 0 Logie operations such as comparison of numbers. In order to execute an instruction, operands need to be brought into the ALU from the memory. i Operands are stored in general purpose registers available in the ALU. i Access times of general purpose registers are faster than the cache. ) Results of the operations are stored back in the memory or retained in the processor for immediate use. How are the functiona connected? ‘For a computer to achieve its operation, the functional units need to communicate with each other. ‘In order to communicate, they need to be connected. Inpu Outpu Memor Process t t y or LL. Tt a saa ‘Functional units may be connected by a group of parallel wires. *The group of parallel wires is called a bus. ‘Each wire in a bus can transfer one bit of information. ‘The number of parallel wires in a bus is equal to the word length of a computer Organization of cache and main memory Mai Cach Process mor emor ye . or |. I Why is the access time of the cache memory lesser than the access time of the main memory? < > Famous Quotes “Future computers may weigh less than 1,5 tn”, (1949) “I believe there is a world market for five computers”, T. Watson, IBM CEO (1943) “There is no particular reason why someone would want a computer at home”, K. Oslon, president of DEC (1974) “640Kbytes of memory should be enough for anybody”, B. Gates, president of Microsoft (1981) Types of Architectures ® von Neumann > Same memory holds data, instructions. > A single set of address/data buses between CPU and memory © Harvard > Separate memories for data and instructions. > Two sets of address/data buses between CPU and memory Von Neumann Architecture Primary Memory CPU (Central Processing Unit) With Control Unit and Arithmetic and Logic Unit This model of the typical digital computer is called the von Neumann compu) > Programs and data are stored in the same memory: primary memo > The computer can only perform one instruction at a time. The von Neumann architecture allows for one instruction to be read from memory or data to be read/written from/to memory at a time. In other words, an instruction fetch and data operation cannot be performed at the same time. Instructions and data are stored in the same memory subsystem and share a communication pathway or bus to the CPU. This constraint is referred to as the von Neumann bottleneck and directly impacts the performance of the system.