Lecture 2 Data processing

Lecture Outline How computers process data CPU architecture Today’s lecture Lecture Outline How computers process data CPU architecture Memory types

Model of a computing Machine ? Model of a computing Machine

Model of a computing machine Computing machine (Computer): “a machine that stores and manipulates information under the control of a changeable program that is stored in its memory.” Pocket calculator: not a computer ! Manipulates information, but is built to do a specific task (no changeable stored program) This model is named the “von Neumann architecture” (John von Neumann – 1945; EDVAC - Electronic Discrete Variable Automatic Computer – the first stored-program computer) Stored-program concept: earlier ideas in theoretical articles of: Alan Turing (1936), Konrad Zuse (1936)

The von Neumann architecture CPU Input Device Output Device ALU CU Secondary storage Main memory (RAM)

The von Neumann architecture Central Processing Unit (CPU): the “brain” of the machine. CU: Control Unit ALU: Arithmetic and Logic Unit Carries out all basic operations of the computer Examples of basic operation: adding two numbers, testing to see if two numbers are equal. Main memory (called RAM for Random Access Memory): stores programs and data Fast but volatile Secondary memory: provides permanent storage Human-computer interaction: through input and output devices. keyboard, mouse, monitor Information from input devices is processed by the CPU and may be sent to the main or secondary memory. When information needs to be displayed, the CPU sends it to the output device(s).

How computers process data ? How computers process data The basis of the processing part of the computer is the binary system, which has only two digits: 1 and 0. These two digits, called bits, correspond to the on and off states of electricity used in computers. A group of 8 bits, called a byte, represents one character in the computer. Storage capacities are expressed in multiples of bytes: about 1,000 bytes = 1 kilobyte; about 1 million bytes = 1 megabyte; about 1 billion bytes = 1 gigabyte; about 1 trillion bytes = 1 terabyte; about 1 quadrillion bytes = 1 petabyte. Letters, numbers, and special characters are represented within a computer by binary coding schemes, such as ASCII, the code most widely used in microcomputers; EBCDIC, used with large computers; and Unicode, a subset of ASCII that uses 16 bits for each character. A parity bit is an extra bit attached to the end of a byte for purposes of checking for accuracy. Each computer brand has its own type of machine language, a binary-type programming language that the computer can run directly, which is why one type of computer can't run the software from another type of computer.

Arithmetic/ Logic Unit (ALU) Central Processing Unit CPU Control Unit Arithmetic/ Logic Unit (ALU)

directs and coordinates most of the computer operations Control Unit directs and coordinates most of the computer operations 4 basic operations: Fetch – obtain a program instruction or data item from memory Decode - translate the instruction into commands Execute - carry out the command Store - write the result to memory The control unit is the circuitry that controls the flow of data through the processor, and coordinates the activities of the other units within it. In a way, it is the "brain within the brain", as it controls what happens inside the processor, which in turn controls the rest of the PC.

Arithmetic and Logic Unit Comparison (greater than, equal to, or less than) Arithmetic (addition, subtraction, multiplication, and division) .and. .not. .or. Logical (AND, OR, NOT) In computing, an arithmetic logic unit (ALU) is a digital circuit that performs arithmetic and logical operations. The ALU is a fundamental building block of the central processing unit (CPU) of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers. The processors found inside modern CPUs and graphics processing units (GPUs) have inside them very powerful and very complex ALUs; a single component may contain a number of ALUs.

Arithmetic/ Logic Unit (ALU) Arithmetic and Logic Unit Performs the execution part of the machine cycle .and. .not. .or. CPU Control Unit Arithmetic/ Logic Unit (ALU)

Machine Cycle 4 operations of the CPU (control unit) comprise a machine cycle; also called an instruction cycle Instruction time– time to fetch and decode Execution time– time to execute and store e-time i-time The shortest interval in which an elementary operation can take place within the processor. It is made up of some number of clock cycles. The computer can only do one thing at a time. Each action must be broken down into the most basic steps. One round of steps from getting an instruction back to getting the next instruction is called the Machine Cycle. An instruction cycle (also called fetch-and-execute cycle, fetch-decode-execute cycle, and FDX) is the time period during which a computer reads and processes a machine language instruction from its memory or the sequence of actions that the central processing unit (CPU) performs to execute each machine code instruction in a program. The name fetch-and-execute cycle is commonly used. The instruction must be fetched from main memory, and then executed by the CPU. This is fundamentally how a computer operates, with its CPU reading and executing a series of instructions written in its machine language. From this arise all functions of a computer familiar from the user's end.

Example Step 4: The results of the math problem are stored in memory The result in memory displays on the screen of the monitor Step 3: The ALU executes the math problem Step 2: The control unit decodes the math problem and sends it to the ALU Step 1: The control unit fetches the math problem from memory A student enters a math problem into the memory of the computer

System Clock Synchronizes all computer operations. A clock "tick" is the smallest unit of time in which processing happens, and is sometimes called a cycle; some types of work can be done in one cycle while others require many. Faster clock speed means the CPU can execute more instructions each second Units: MHz and GHz

CPU Registers High speed memory in CPU that stores: Temporary storage location used by the CPU High speed memory in CPU that stores: Instruction while being decoded Location from where instruction was fetched Data while the ALU processes it Results of a calculation

Memory volatile memory nonvolatile memory Volatile Memory Loses its contents when the computer's power is turned off Volatile Memory Loses its contents when the computer's power is turned off nonvolatile memory Does not lose its contents when the computer’s power is turned off

2 basic types of RAM chips Memory 2 basic types of RAM chips Dynamic RAM (DRAM) Also called main memory Most common type Static RAM (SRAM) Used for special applications such as cache Faster and more reliable than DRAM chips Variations: Synchronous DRAM (SDRAM) SDRAM refers to synchronous dynamic random access memory, a term that is used to describe dynamic random access memory that has a synchronous interface. Traditionally, dynamic random access memory (DRAM) has an asynchronous interface which means that it responds as quickly as possible to changes in control inputs. SDRAM has a synchronous interface, meaning that it waits for a clock signal before responding to control inputs and is therefore synchronized with the computer's system bus. The clock is used to drive an internal finite state machine that pipelines incoming instructions. This allows the chip to have a more complex pattern of operation than asynchronous DRAM which does not have a synchronized interface. Static random access memory (SRAM) is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM (DRAM), it does not need to be periodically refreshed, as SRAM uses bistable latching circuitry to store each bit. SRAM exhibits data remanence,[1] but is still volatile in the conventional sense that data is eventually lost when the memory is not powered. The term SDRAM, which stands for synchronous DRAM, should not be confused with SRAM. Double data rate SDRAM (DDR SDRAM or SDRAM II) Direct Rambus® DRAM (Direct RDRAM®)

Also called cache store or RAM cache Memory Cache Also called cache store or RAM cache Limited very fast memory Lower access time Stores frequently used instructions/ data to speed up processing When the processor needs an instruction or data, it first searches cache. If it cannot locate the item in cache, then it searches RAM.

(basic input/output system) Read Only Memory (ROM) Fixed start-up instructions BIOS (basic input/output system) Stored on ROM Non-volatile Read-only

Flash Memory Nonvolatile EEPROM (Electrically Erasable Programmable Read-Only Memory) memory that can be erased and reprogrammed Stores data and programs on many handheld computers and devices Flash memory is non-volatile computer memory that can be electrically erased and reprogrammed. It is a technology that is primarily used in memory cards and USB flash drives for general storage and transfer of data between computers and other digital products. It is a specific type of EEPROM (Electrically Erasable Programmable Read-Only Memory) that is erased and programmed in large blocks; in early flash the entire chip had to be erased at once. Flash memory costs far less than byte-programmable EEPROM and therefore has become the dominant technology wherever a significant amount of non-volatile, solid state storage is needed. Example applications include PDAs (personal digital assistants), laptop computers, digital audio players, digital cameras and mobile phones. It has also gained popularity in the game console market, where it is often used instead of EEPROMs or battery-powered SRAM for game save data.

What are the different CPU Architectures ? What are the different CPU Architectures Computer architecture in computer engineering is the conceptual design and fundamental operational structure of a computer system. It was founded and created by Don Annaway. It is a blueprint and functional description of requirements (especially speeds and interconnections) and design implementations for the various parts of a computer — focusing largely on the way by which the central processing unit (CPU) performs internally and accesses addresses in memory.

Name common microprocessors ? Name common microprocessors Intel Pentium® Pentium® II with MMX™ Celeron™ Xeon™ Itanium™ Used in PCs AMD (Intel-compatible) Duron™ AMD-K6® Athlon™ with 3DNow! ™ Used in PCs Motorola PowerPC Used in Apples Alpha Used in workstations and high-end servers The basis of the processing part of the computer is the binary system, which has only two digits: 1 and 0. These two digits, called bits, correspond to the on and off states of electricity used in computers. A group of 8 bits, called a byte, represents one character in the computer. Storage capacities are expressed in multiples of bytes: about 1,000 bytes = 1 kilobyte; about 1 million bytes = 1 megabyte; about 1 billion bytes = 1 gigabyte; about 1 trillion bytes = 1 terabyte; about 1 quadrillion bytes = 1 petabyte. Letters, numbers, and special characters are represented within a computer by binary coding schemes, such as ASCII, the code most widely used in microcomputers; EBCDIC, used with large computers; and Unicode, a subset of ASCII that uses 16 bits for each character. A parity bit is an extra bit attached to the end of a byte for purposes of checking for accuracy. Each computer brand has its own type of machine language, a binary-type programming language that the computer can run directly, which is why one type of computer can't run the software from another type of computer.

Von Neumann Architecture How Computer process data CPU ALU Lecture’s Summary Von Neumann Architecture How Computer process data CPU ALU Memory: RAM (DRAM/ SRAM)/ Cache RAM, ROM & Flash Memory CPU Architecture

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