<ul><li>Machine Cycle Definition</li></ul>A machine cycle, also called a processor cycle or a instruction cycle, is the basic operation performed by a central processing unit (CPU). A CPU is the main logic unit of a computer. A machine cycle consists of a sequence of three steps that is performed continuously and at a rate of millions per second while a computer is in operation. They are fetch, decode and execute. There also is a fourth step, store, in which input and output from the other three phases is stored in memory for later use; however, no actual processing is performed during this step. In the fetch step, the control unit requests that main memory provide it with the instruction that is stored at the address (i.e., location in memory) indicated by the control unit's program counter. The control unit is a part of the CPU that also decodes the instruction in the instruction register. A register is a very small amount of very fast memory that is built into the CPU in order to speed up its operations by providing quick access to commonly used values; instruction registers are registers that hold the instruction being executed by the CPU. Decoding the instructions in the instruction register involves breaking the operand field into its components based on the instructions opcode. Opcode (an abbreviation of operation code) is the portion of a machine language instruction that specifies what operation is to be performed by the CPU. Machine language, also called machine code, refers to instructions coded in patterns of bits (i.e., zeros and ones) that are directly readable and executable by a CPU. A program counter, also called the instruction pointer in some computers, is a register that indicates where the computer is in its instruction sequence. It holds either the address of the instruction currently being executed or the address of the next instruction to be executed, depending on the details of the particular computer. The program counter is automatically incremented for each machine cycle so that instructions are normally retrieved sequentially from memory. The control unit places these instructions into its instruction register and then increments the program counter so that it contains the address of the next instruction stored in memory. It then executes the instruction by activating the appropriate circuitry to perform the requested task. As soon as the instruction has been executed, it restarts the machine cycle, beginning with the fetch step. <br />Word (computing)/ Word size<br />In computing, word is a term for the natural unit of data used by a particular computer design. A word is simply a fixed sized group of bits that are handled together by the system. The number of bits in a word (the word size or word length) is an important characteristic of computer architecture.<br />The size of a word is reflected in many aspects of a computer's structure and operation; the majority of the registers in the computer are usually word sized and the amount of data transferred between the processing part computer and the memory system, in a single operation, is most often a word. The largest possible address size, used to designate a location in memory, is typically a hardware word (in other words, the full sized natural word of the processor, as opposed to any other definition used on the platform).<br />Modern computers usually have a word size of 16, 32 or 64 bits but many other sizes have been used, including 8, 9, 12, 18, 24, 36, 39, 40, 48 and 60 bits. The slab is an example of a system with an earlier word size. Several of the earliest computers used the decimal base rather than binary, typically having a word size of 10 or 12 decimal digits and some early computers had no fixed word length at all.<br />The size of a word is sometimes defined to be a particular value for compatibility with earlier computers. The most common microprocessors used in personal computers (for instance, the Intel Pentiums and AMD Athlons) are an example of this; their IA-32 architecture is an extension of the original Intel 8086 design which had a word size of 16 bits. The IA-32 processors still support 8086 (x86) programs, so the meaning of word in the IA-32 context was kept the same, and is still said to be 16 bits despite the fact that they at times (especially when the default operand size is 32 bits) operate largely like a machine with a 32 bit word size, similarly in the newer x86-64 architecture a word is still 16 bits, although 64-bit (quadruple word) operands may be more common.<br />3429007620<br />The larger the word and the faster the computer calculates and compares. However, the speed increase depends on the size of the data being calculated. Adding a 16-bit number will not be faster in a computer with 32-bit registers than one with 16 bits, but a 24-bit number will be faster. The 16-bit computer requires additional steps to deal with the 24 bits (16 bits first, then the remaining 8), whereas all 24 bits of the number can fit in the 32-bit register. <br /> <br />** Word Size<br />The word size used in a computer is generally limited to an economical size but involves the memory size, Size of the instruction set, and precision put required in the computer.<br />Memory Size<br />The number of bits required to address the number of memory locations must be taken into account in setting the computer word size. While systems can be built which use multiple words or selected word parts to contain a memory address, this usually leads to involved addressing equipment and adds to the cost or running time of the machine.<br />Instruction Count<br />The word size must be large enough to accommodate the number of instructions which are required to do the things that are required of the machine. There are all kinds of possible processing jobs which may be made part of a computer these special instructions can lead to oversize and expensive computers. One extreme example of this is a computer which had a record gather and a record scatter instruction couplet. This is useful for working with records to be sorted and made up into reports, but was of little use for my scientific computations. On the other hand, I would have liked to have a square root instruction for my scientific work. How ever the instruction set size must be taken into account in setting a computer's word size. HYPERLINK "
Go to Special Instructions<br />Data Precision<br />The required data precision is of primary concern when establishing word size. Present day practice limits word size to multiples of eight bit byte sizes by the convention established to drive printers and other output devices. Early computers used as little as six bits for storage of alphabetic information and consequently had multiples of six bit word sizes. Other formats are possible, such as BCD method of storing all numbers in floating point form as was used by the ATARI home computer which storedall numbers with a ten digit format and with a power of ten exponent. Common specifications to day lead to a word size of 32 bits or 64 bits for very high precision. Smaller word sizes may be used for specific purposes.<br />Computer Architecture<br />In computer science and computer engineering, computer architecture or digital computer organization is the conceptual design and fundamental operational structure of a computer system. It is a blueprint and functional description of requirements 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.<br />It may also be defined as the science and art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals.<br />Computer architecture comprises at least three main subcategories: HYPERLINK "
<br />Instruction set architecture, or ISA, is the abstract image of a computing system that is seen by a machine language (or assembly language) programmer, including the instruction set, word size, memory address modes, processor registers, and address and data formats.<br />Micro architecture, also known as Computer organization is a lower level, more concrete and detailed, description of the system that involves how the constituent parts of the system are interconnected and how they interoperate in order to implement the ISA. The size of a computer's cache for instance, is an organizational issue that generally has nothing to do with the ISA.<br />System Design which includes all of the other hardware components within a computing system such as:<br />System interconnects such as computer buses and switches<br />Memory controllers and hierarchies<br />CPU off-load mechanisms such as direct memory access (DMA)<br />Issues like multiprocessing.<br />Once both ISA and microarchitecture have been specified, the actual device needs to be designed into hardware. This design process is called implementation. Implementation is usually not considered architectural definition, but rather hardware design engineering.<br />Implementation can be further broken down into three (not fully distinct) pieces:<br />Logic Implementation — design of blocks defined in the microarchitecture at (primarily) the register-transfer and gate levels.<br />Circuit Implementation — transistor-level design of basic elements (gates, multiplexers, latches etc) as well as of some larger blocks (ALUs, caches etc) that may be implemented at this level, or even (partly) at the physical level, for performance reasons.<br />Physical Implementation — physical circuits are drawn out, the different circuit components are placed in a chip floorplan or on a board and the wires connecting them are routed<br />4. Define the ff.<br /> Motherboard - A motherboard is the central printed circuit board (PCB) in many modern computers and holds many of the crucial components of the system, while providing connectors for other peripherals.<br />Slot - An opening in a computer where you can insert a printed circuit board. Slots are often called expansion slots because they allow you to expand the capabilities of a computer. The boards you insert in HYPERLINK "
expansion slots<br />are called expansion boards or add-on boards.<br />BUS - An electronic pathway. In networks, a configuration (topology) with a single linear cable, terminated at each end, to which computers and devices are connected. There are no loops or branches in the cable. Also called a daisy chain. <br />Network - A network is a collection of terminals, computers, servers, and components which allows for the easy flow of data and use of resources between one another.<br />Signal - In electronics, a signal is an electric current or electromagnetic field used to convey data from one place to another. The simplest form of signal is a direct current (DC) that is switched on and off; this is the principle by which the early telegraph worked. More complex signals consist of an alternating-current (AC) or electromagnetic carrier that contains one or more data streams.<br />Local Area Network - a local computer network for communication between computers; especially a network connecting computers and word processors and other electronic office equipment to create a communication system between offices<br />Wide Area Network - A network that includes computers spread across a large geographical distance, usually involving several cities, states or countries. Communications connections in a WAN are typically done over modems, T1 lines, or satellite hookups.<br />Network Server - LANs use a powerful microcomputer with a large disk capacity as a file server or network server. The server handles resource sharing and telecommunications.<br />Work station - A workstation is a high-end microcomputer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems. <br />Host - In computer networking, a network host, Internet host, host, or Internet node is a computer connected to the Internet - or more generically - to any type of data network. A network host can host information resources as well as application software for providing network services.<br /><ul><li>Network Topologies</li></ul>Network topology is defined as the interconnection of the various elements (links, nodes, etc.) of a computer network. Network Topologies can be physical or logical. Physical Topology means the physical design of a network including the devices, location and cable installation. Logical topology refers to the fact that how data actually transfers in a network as opposed to its physical design.<br />Physical topologies<br />The mapping of the nodes of a network and the physical connections between them – i.e., the layout of wiring, cables, the locations of nodes, and the interconnections between the nodes and the cabling or wiring system<br />Signal topology<br />The mapping of the actual connections between the nodes of a network, as evidenced by the path that the signals take when propagating between the nodes.<br />Logical topology<br />The logical topology, in contrast to the "
, is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices. A network's logical topology is not necessarily the same as its physical topology. For example, twisted pair Ethernet is a logical bus topology in a physical star topology layout. While IBM's Token Ring is a logical ring topology, it is physically set up in a star topology.<br />