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ASCII means American Standard Code for Information Interchange. It is an industry standard, which assigns letters, numbers, and other characters within the 256 slots available in the 8 bit code. The ASCII table is divided in 3 sections: *Non printable system codes between 0 and 31. *"Lower ASCII" between 32 and 127. This part of the table originates from older, American ADP systems, which work d on 7 bit character tables. Foreign letters, like Ø and Ü were not available then. *"Higher ASCII" between 128 and 255. This part is programmable, in that you can exchange characters, based on which language you want to write in. Foreign letters are placed in this part. An example Let us imagine a stream of bits sent from the keyboard to the computer. When you type, streams of 8 bits are sent to the computer. Let us look at a series of bits: 001100010011001000110011 Bits are combined into bytes (each 8 bits). These 24 bits are interpreted as three bytes. Let us read them as bytes: 00110001, 00110010, and 00110011. When we convert these byte binary numbers to decimal numbers, you will see that they read as 49, 50, and 51 in decimal numbers. To interpret these numbers, we have to look at the ASCII table. You will find that you have typed the numbers 1, 2, and 3.
CMOS (Complimentary Metal Oxide Semiconductor) is a small amount of memory in a special RAM chip. Its memory is maintained with electric power from a small battery. Certain system data are stored in this chip. They must be read to make the PC operable. There may be 100 to 200 bytes of data regarding date, time, floppy and hard disk drives, and much more. CMOS data can be divided in two groups: * Data, which POST can not find during the system test. * Data, which contain user options. For example, POST cannot by itself find sufficient information about the floppy drive(s). Floppy drives are so "dumb," that POST cannot read whether they are floppy drives or not, nor what type. About the same goes for IDE hard disks, while EIDE hard disks are a little more "intelligent," However, POST still needs assistance to identify them 100% correctly. The same goes for RAM: POST can count how much RAM is in the PC. However, POST cannot detect whether it is FPM, EDO or SD RAM. Since the CPU and BIOS reads data from RAM chips differently, depending on the RAM type, that type must be identified. Configuration The PC must be configured, be supplied with this information. That is done in the factory or store, where it is assembled. This information is stored in CMOS, where they stay. CMOS data only need to be updated, when different or additional hardware components are installed. This could be a different type hard disk or floppy disks or an new RAM type, Often he user can do this. Other data in CMOS contain various user options. Those are data, which you can write to CMOS. For example, you can adjust date and time, which the PC then adjusts every second. You can also choose between different system parameters. Maybe you want a short system check instead of a long one. Or if you want the PC to try to boot from hard disk C before trying floppy disk A, or vice versa. These options can be written to CMOS. Many of the options are of no interest to the ordinary user. These are options, which regard controller chips on the system board, which can be configured in different ways. Ordinarily, there is no need to make such changes. The system board manufacturer has already selected the optimal configurations. They recommend in their manuals, that you do not change these default settings. We can conclude, that CMOS data are essential system data, which are vital for operation of the PC. Their special feature is,
Twisted pair cable consists of two insulated cupper wires twisted together. It is used in telephone line for voice and data communications. Coaxial cable has the following layers: a metallic rod-shaped inner conductor, an insulator covering the rod, a metallic outer conductor (shield), an insulator covering the shield, and a plastic cover.Coaxial cable can carry signals of higher frequency ranges than twisted-pair cable. Coaxial cable is used in cable TV networks and Ethernet LANs.Fiber-optic cables are composed of a glass or plastic inner core surrounded by cladding, all encased in an outer jacket.Fiber-optic cables carry data signals in the form of light. The signal is propagated along the inner core by reflection. Its features are noise resistance, low attenuation, and high bandwidth capabilities. It is used in backbone networks, cable TV nerworks, and fast Ethernet networks.
The big, heavy traditional monitors will eventually be phased out. They will be replaced by the thin and "soft" LCD (Liquid Crystal Display) screens! It may be a few years before this technology will be dominating, but it is bound to happen. The LCD screens are excellent, and actually they are already available. The LCD screen is flat, since it contains no cathode ray tube (CRT). In stead the screen image is generated on a flat plastic disk. Here you see a Siemens Nixdorf 3501T. It produces a sharp high resolution image - better than any others I have seen. LCD screens are also called "soft" screens, since their images have a softer quality than those from traditional CRT monitors. The image does not flicker thus causing less eye strain. People who have become accustomed to these soft images will not return to the traditional monitors. At the same time the LCD screen is by far the most environmentally safe product. These flat screens emit zero radiation, and they consume significantly less power than the traditional monitors. Another reason to expect LCD screens to become the monitors of the future.
Network interface cards, commonly referred to as NICs, and are used to connect a PC to a network. The NIC provides a physical connection between the networking cable and the computer's internal bus. Different computers have different bus architectures; PCI bus master slots are most commonly found on 486/Pentium PCs and ISA expansion slots are commonly found on 386 and older PCs. NICs come in three basic varieties: 8-bit, 16-bit, and 32- bit. The larger the number of bits that can be transferred to the NIC, the faster the NIC can transfer data to the network cable. Many NIC adapters comply with Plug-n-Play specifications. On these systems, NICs are automatically configured without user intervention, while on non-Plug-n-Play systems, configuration is done manually through a setup program and/or DIP switches. Cards are available to support almost all networking standards, including the latest Fast Ethernet environment. Fast Ethernet NICs are often 10/100 capable, and will automatically set to the appropriate speed. Full duplex networking is another option, where a dedicated connection to a switch allows a NIC to operate at twice the speed.
This chip was developed by Intel in Haifa, Israel. The processor is super scalar, meaning that it can execute more than one instruction per clock tick. Typically, it handles two instructions per tick. In this respect, we can compare it to a double 486. At the same time there have been big changes in the system bus: the width is doubled to 64 bit and the speed is increased to 60 or 66 MHZ. This results in a substantial improvement from the 486 technology. Originally, Pentium came in two versions: a 60 MHZ and a 66 MHZ. Both operated on 5 Volt. This produced a lot of heat (it was said that you could fry an egg on them!) The next Pentium (P54C) generation had a built in 1½ clock doubling, and ran at 3½ Volt. This took care of the heat problem. Since then, Intel carried two Pentium lines: those which run at 60 MHZ on the system bus (P90, P120, P150, and P180) and the best, which run at 66 MHZ (P100, P133, P166 and P200).
On July 26th 1998 Intel will introduce a new Pentium II edition. The processor is named Pentium II Xeon. It will require a new version of Slot One (Slot Two). The module will have the same dimensions as the current Pentium II, but there are a few important innovations and improvements: * The CPU will mounted in a new Slot Two with three layers of edge connectors. 100 MHZ system bus with clock doubling 4.0 and 4.5 (meaning 400/450 MHZ clock speed internally). * New type L2 cache: CSRAM, which can run at full CPU speed. *512, 1,024, or 2,048 KB L2 RAM. * Up to 4 GB RAM can be in cache. The Xeon chip is for high performance servers. The first topmodel will hold 2 MB L2 cache on the cartridge, running at full 450 MHZ. This chip will cost $4,500!
MMX is a new set of instructions (57 new integer instructions, four new data types, and eight 64 bit registers), which expand the capabilities of the CPU. It is an addition to the original Pentium set of instructions. The new instructions are designed for multimedia programs. The programmers can utilize these instructions in their programs. These allow the Pentium to provide improved program execution. MMX is a new standard, which Intel will include in all their CPU's. Both Cyrix and AMD use MMX in their 6th generation CPU's (K6 and M2). Programs, which are written with MMX instructions, can still be run on, for example, a Pentium without MMX. However, execution is slower with the traditional instructions.
->The concept of a logical address space that is bound to a separate physical address space is central to proper memory management. Logical address – generated by the CPU; also referred to as virtual address. Physical address – address seen by the memory unit. ->Logical and physical addresses are the same in compile-time and load-time address-binding schemes; logical (virtual) and physical addresses differ in execution-time address-binding scheme
1. Check if it is taking longer than usual to start up 2. Check if it is slow with one / any particular application or slow overall. 3. Check for Spyware/Malware/Virus in the computer 4. Check the available Hard-Disk Drive Space in the computer.
Generally, there are 04 lights. They indicate the following: 1. Power Light: Shows if the device (Modem)is getting Power Supply or not. 2. Link Light: Indicates if the device is getting broadband/internet signals properly from the ISP 3. Data Light: Indicates wether the internet is working or not. 4. Connectivity Light: Indicates the Modem is connected to a PC or not.
Some of the commonly available ports in a Computer are as follows: 1. Keyboard & Mouse Ports – Also known as PS/2 ports 2. USB Ports 3. VGA Ports 4. Sound Ports 5. LAN Port – Also known as Ethernet Port
Process Termination: ->Abort all deadlocked processes. ->Abort one process at a time until the deadlock cycle is eliminated. ->In which order should we choose to abort? Priority of the process. How long process has computed, and how much longer to completion. Resources the process has used. Resources process needs to complete. How many processes will need to be terminated? Is process interactive or batch? Resource Preemption: ->Selecting a victim – minimize cost. ->Rollback – return to some safe state, restart process for that state. ->Starvation – same process may always be picked as victim, include number of rollback in cost factor.
ROMwas described earlier as being nonvolatile, meaning that it holds its contents without a power source. The opposite of nonvolatile is volatile. Volatile memory cannot hold its contents, the data, or programs placed on it without an active power source, such as a wall socket or battery. RAM is a volatile form or memory and when it loses its power, it loses its contents. If you have ever lost everything you were working on when a power failure hit, someone tripped over the power cord, or you had to reboot the PC, then you’ve experienced the downside of volatile memory. So, why is volatile memory used in the PC? Why not just use nonvolatile memory? If you were to use EEPROMs or any of the newer types of SRAM (see the section “RAM Types” later in this section), the cost for the amount of memory you need to run the high-graphic and feature-rich software of today would exceed that of the entire rest of the PC, including all of the options and bells and whistles you could add. Volatile RAM is inexpensive, readily available, easily expanded, and, as long as you protect your system against power problems, it is error- and trouble-free for the most part.
10Base2— An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling, with a contiguous cable segment length of 100 meters and a maximum of 2 segments. 10Base5—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling, with 5 continuous segments not exceeding 100 meters per segment. 10BaseT—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling and twisted pair cabling.
As I wrote in module 4a, drives are storage media, which can hold a file system. When a disk is formatted in a drive, it becomes organized and prepared to receive data. When we format a disk, it receives a file system. Formatting can be compared to starting a library. You must install the book shelves and the catalogue system before any books are put in place. Once the library is ready, bring on the books! Similarly with a disk. When we format it, we "burn in" a file system to make it ready to receive data (files). We can format with any one of several different file systems: *FAT (File Allocation Table), the original, old 16 bit DOS system is probably used in 90% of all PC’s. It is also called FAT16 contrary to: *FAT32 a new addition to FAT, which Microsoft introduced with Windows 95 B – The December -96 version (OSR2). *HPFS (High Performance File System) from OS/2. It is an advanced 32 bit file system, which in all respects is far superior to FAT, except for possible usage. It can only be used with OS/2. *NTFS from Windows NT. A 32 bit file system like HPFS, but not compatible with it. NTFS can, unfortunately, only be used in Windows NT. If it was available for use in Windows 95, it would be far to preferable to FAT and FAT32. *NetWare is a server operating system from Novell. It has its own 32 bit file system. For that reason, the Novell server, contrary to NT or OS/2 servers, cannot be used as a work station. The file system is much faster than FAT, but it works only with Novell servers (typically file servers). * UNIX servers have their own filing system. Here the use of upper/lower case in file naming is significant. Read in the following pages about the concepts of these file systems.
Operating system controls and coordinates the use of the hardware among the various applications programs for various uses. Operating system acts as resource allocator and manager. Since there are many possibly conflicting requests for resources the operating system must decide which requests are allocated resources to operating the computer system efficiently and fairly. Also operating system is control program which controls the user programs to prevent errors and improper use of the computer. It is especially concerned with the operation and control of I/O devices.
Repeater: Also called a regenerator, it is an electronic device that operates only at physical layer. It receives the signal in the network before it becomes weak, regenerates the original bit pattern and puts the refreshed copy back in to the link. Bridges: These operate both in the physical and data link layers of LANs of same type. They divide a larger network in to smaller segments. They contain logic that allow them to keep the traffic for each segment separate and thus are repeaters that relay a frame only the side of the segment containing the intended recipent and control congestion. Routers: They relay packets among multiple interconnected networks (i.e. LANs of different type). They operate in the physical, data link and network layers. They contain software that enable them to determine which of the several possible paths is the best for a particular transmission. Gateways: They relay packets among networks that have different protocols (e.g. between a LAN and a WAN). They accept a packet formatted for one protocol and convert it to a packet formatted for another protocol before forwarding it. They operate in all seven layers of the OSI model.
The disadvantages of fiber optics cable over twisted pair cable are Cost-It is expensive Installation/maintenance-Any roughness or cracking defuses light and alters the signal Fragility-It is more fragile
Expensive but good: SCSI makes the PC a little more expensive, but much better. That's all. The advantages are, that on the same PC you have free access to use many units and good hard disks: *It is easy to add many high end accessories, such as DAT-streamers, CD-ROM recorders, MO drives, scanners, etc. *You can use SCSI hard disks. *You can use CD-ROM drives on SCSI , where they perform a lot better than on IDE. Advantages of SCSI hard disks SCSI hard disk are generally of higher quality than other disks. EIDE disks come in various qualities from different manufacturers. However, even the best EIDE disks cannot compete with the best SCSI disks. Typically, good SCSI disks come with a 5 year warranty. They come in larger capacities than the EIDE disks and they are faster. At 5400, 7200 or 10.000 RPM they have shorter seek times. They also have a bigger cache. Another advantage is the large number of accessories, which can be attached. If you buy a 4 GB SCSI disk today, you will guaranteed need additional disk storage in a few years. Then you just add disk number two to the SCSI chain, and later number three. The system is more flexible than EIDE, where you can have a maximum of four units incl. CD-ROM. The SCSI hard disks can also adjust the sequence in the PC's disk read commands. This allows to read the tracks in an optimal sequence, enabling minimal movements of the read/write head. Quantum calls this technology ORCA (Optimized Reordering Command Algorithm). It should improve performance by 20%. Finally, the SCSI controller can multitask, so the CPU is not locked up during hard disk operations, which you can experience with IDE. SCSI hard disks can achieve substantially larger transfer capacity than the IDE drives, but they have the same bottle necks: the serial handling of bits in the read/write head, where the capacity is highly dependent on the rotation speed.
It is a wireless LAN technology designed to connect devices of different functions such as telephones, notebooks, computers, cameras, printers and so on. Bluetooth LAN Is an adhoc network that is the network is formed spontaneously? It is the implementation of protocol defined by the IEEE 802.15 standard.
The point to point protocol was designed to provide a dedicated line for users who need internet access via a telephone line or a cable TV connection. Its connection goes through three phases: idle, establishing, authenticating, networking and terminating. At data link layer it employs a version of HDLC.
I/O busses connect the CPU to all other components, except RAM. Data are moved on the busses from one component to another, and data from other components to the CPU and RAM. The I/O busses differ from the system bus in speed. Their speed will always be lower than the system bus speed. Over the years, different I/O busses have been developed. On modern Pentium PC's, you will find at least two significant busses, and one less significant: *The ISA bus, which is an older low speed bus. *The PCI bus, which is a new high speed bus. * The USB bus (Universal Serial Bus), which is a new low speed bus. As mentioned earlier, I/O busses are really derivatives from the system bus. On the system board it ends in a controller chip, which forms a bridge to the two other busses. The essential in modern PC's is fast busses. Let us compare the two primary I/O busses: Bus Transmission time Data volume per transmission ISA 375 ns 16 bit PCI 30 ns 32 bit Clearly, there is a vast difference between the capacity of the two busses. All in all, the busses have a very central placement in the PC's data exchange. Actually, all components except the CPU communicate with each other and with RAM via the different I/O busses.
When we speak about busses and system boards, we are also speaking about chip sets. The chip sets are a bunch of intelligent controller chips, which are on any system board. They are closely tied to the CPU, in that they control the busses around the CPU. Without the chip sets, neither RAM or I/O busses could function together with the CPU. New technologies - new chip set Therefore, the chip sets are quite central components on the system boards. When new technological features are introduced (and this happens continuously) they are often accompanied by new chip sets. The new chip sets often enable: * Higher speed on one or more busses * Utilization of new facilities (new RAM types, new busses, improved EIDE, etc.) There are several suppliers of Pentium chip sets: *Intel *SIS * Opti * Via * AMD Intel has hitherto been the leader in supplying chip sets to the Pentium system board. Therefore, let us just mention their chip sets, which have astronomical names. The Neptune chip set (82434NX) was introduced in June 1994. It replaced the Mercury set (82434LX). In both chip sets, there were problems with the PCI bus. In January 1995 Intel introduced the first Triton , where everything worked. This chip set supports some new features: it supports EDO RAM, and it offers bus master integrated EIDE control and NSP (Native Signal Processing - one of the many new creations, which was soon forgotten).
The CPU is centrally located on the system board. Since the CPU carries out a large share of the work in the computer, data pass continually through it. The CPU continually receives instructions to be executed. Each instruction is a data processing order. The work itself consists mostly of calculations and data transport. Data have a path to the CPU. It is kind of a data expressway called the system bus. You will hear much more about this later.
When the first installation of Windows fails to boot for some reason, another copy of Windows is installed in teh same drive but in a different directory (so that the customer can access to and backup his old data). This is called Parallel Installation of Windows.
Ans :When a process requests an available resource, system must decide if immediate allocation leaves the system in a safe state ->System is in safe state if there exists a safe sequence of all processes. ->Sequence is safe if for each Pi, the resources that Pi can still request can be satisfied by currently available resources + resources held by all the Pj, with j If Pi resource needs are not immediately available, then Pi can wait until all Pj have finished. When Pj is finished, Pi can obtain needed resources, execute, return allocated resources, and terminate. When Pi terminates, Pi+1 can obtain its needed resources, and so on. ->Deadlock Avoidance Þ ensure that a system will never enter an unsafe state.
A new bus has arrived on the PC. It is called AGP (Advanced Graphics Port). It is exclusively designed for video cards AGP will probably not be in widespread use before 1998. Amongst other things, the system must be supported by the operating system (Windows 98). Likewise, it is claimed that the system bus will be raised from the current 66 MHZ to 100 MHZ, to allow AGP to prove its worth. AGP includes several techniques, of which two are understandable: * PCI version 2.1 with 66 MHZ bus frequency. That is a doubling of transfer speed Possibility to utilize system board RAM for texture cache. This will reduce RAM card demand in connection with the most demanding programs. *One big AGP advantage is that the PCI bus is relieved of work with graphics data. It can concentrate on other demanding transport duties, like transfer to and from network adapter and disk drives. Here you see the AGP-socket at the bottom. It looks like a PCI-socket, but it has been placed in a different position on the board. In the top you see two (black) ISA-sockets. Then four (white) PCI-sockets, and then the brown AGP-socket:
The operating system can be evaluated from different angles: An operating system is a number of files, which are read from the hard disk at the end of of the PC start-up routine. An operating system is a program layer. It connects to the the PC hardware, to facilitate optimal execution of the user programs. The first definition does not say much. Let us start with the second: The operating systems links software and hardware together. It has to enable user programs, like Works, Office, etc., to function with all possible hardware configurations. You can imagine the relationship between hardware and user programs thus: Hardware is clumsy and dissimilar. There are untold variations of PC's. They can have one or another type hard disk, CPU, video card, etc. All of these various PC configurations behave each in their own way. The use programs are 100% similar. They are off the shelf products, which expect the PC to respond in a certain manner. How do we make these two layers work together? Can we eliminate out the differences in the PC hardware, so a standard product like Works just functions? Yes we can. We read in an operating system - a system layer, which smoothes out and standardizes the hardware: You should understand the operating system as a necessary layer, which smoothes out bumps and pot holes in your PC's hardware. This will give the user programs a stable, even work platform.
BIOS stands for Basic Input-Output System and is pronounced as “Bye-Ose“. The BIOS is available on all the computers. It makes sure that all the components of the computer can function together. It has information about all the hardware components in the Computer. BIOS can also be called as a Special Software that interfaces the major hardware components of a computer with the Operating System. It is usually stored in a Flash Memory Chip on the Motherboard. Some functions of BIOS: • Performs a POST (Power-On Self Test) for all the different Hardware Components in the System to make sure everything is working properly. • Activating other BIOS Chips on different cards installed in the computer, for example, SCSI and Graphics Cards. • Provides a set of low-level suiting that the Operating System uses to interface different Hardware devices. • BIOS manages things in your computer like the Keyboard, Monitor, Serial and Parallel Ports especially when the computer is Booting up. • Manage the settings for Hard-disk drives, System Clock etc.
The CPU works on two frequencies: An internal and an external. The external clock frequency (the bus frequency) is the speed between the CPU and RAM. In the Pentium CPU's it is actually the speed between L1 and L2 cache. In the Pentium II it is the speed between L2 cache and RAM. * The internal clock frequency is the speed inside the CPU, that is between L1 cache and the various CPU registers. For practical reasons you let these two frequencies depend on each other. In practice you choose a given bus frequency (between 60 and 100 MHz) and double it up a number of times (between 1½ and 5). The latter frequency become the CPU internal work frequency. Here I show a number of theoretical CPU frequencies, resulting form different clock doublings: Many of these frequencies will actually never be used, but they are possible because of the system structure: Bus frequencies Clock doubling factors Resulting CPU frequencies60 MHz1?, 2, 2?, 3, 3?, 4, 4?, 590 MHz, 100 MHz, 120 MHz 66 MHz 133 MHz, 150 MHz, 166 MHz, 75 MHz 180 MHz, 200 MHz, 210 MHz, 83 MHz 225 MHz, 233 MHz, 240 MHz, 100 MHz 250 MHz, 262 MHz, 266 MHz,290 MHz, 300 MHz, 333 MHz,350 MHz, 375 MHz, 415 MHz,450 MHz, 500 MHz Note an important point: The CPU frequency is the result of the the bus frequency multiplied with a factor. If you increase the bus frequency, it affects the CPU frequency, which is also increased. Look here at a page from the manual to a ASUS P2L97 motherboard. It has a clear instruction about how to set the the two values (bus frequency and clock factor).
A computer is made up of multiple parts that either send or receive information. All computers include the following hardware: Computer case: The case that holds all the electronic components of the computer, including the hard disk, RAM chips, central processing unit (CPU), and motherboard. Inside the case is where everything takes place. Monitor: Similar to a television, the monitor displays text, pictures, and other items from the computer on a screen. Keyboard: The set of typewriter-like keys you use to type information into the computer. Mouse: The device that controls the movement of the pointer displayed on the screen. You use the mouse pointer to select and open items on the computer. Disk drive: A device that reads data from and writes data to a disk. A DVD-ROM drive reads both CD-ROMs and DVD-ROMs. A DVD-ROM drive has the words compact disc on the front. The Zip and floppy disk drives look similar, but the Zip disk drive has a larger opening since Zip disks are larger. You can save files such as letters, pictures, and presentations on either Zip or floppy disks. Zip disks can store more information than floppy disks (100 to 250 MB on a Zip disk versus 1.44 MB on a floppy disk). However, a Zip disk costs more than a floppy disk.
Multi programming: Multiprogramming is the technique of running several programs at a time using timesharing. It allows a computer to do several things at the same time. Multiprogramming creates logical parallelism. The concept of multiprogramming is that the operating system keeps several jobs in memory simultaneously. The operating system selects a job from the job pool and starts executing a job, when that job needs to wait for any i/o operations the CPU is switched to another job. So the main idea here is that the CPU is never idle. Multi tasking: Multitasking is the logical extension of multiprogramming .The concept of multitasking is quite similar to multiprogramming but difference is that the switching between jobs occurs so frequently that the users can interact with each program while it is running. This concept is also known as time-sharing systems. A time-shared operating system uses CPU scheduling and multiprogramming to provide each user with a small portion of time-shared system. Multi threading: An application typically is implemented as a separate process with several threads of control. In some situations a single application may be required to perform several similar tasks for example a web server accepts client requests for web pages, images, sound, and so forth. A busy web server may have several of clients concurrently accessing it. If the web server ran as a traditional single-threaded process, it would be able to service only one client at a time. The amount of time that a client might have to wait for its request to be serviced could be enormous. So it is efficient to have one process that contains multiple threads to serve the same purpose. This approach would multithread the web-server process, the server would create a separate thread that would listen for client requests when a request was made rather than creating another process it would create another thread to service the request. To get the advantages like responsiveness, Resource sharing economy and utilization of multiprocessor architectures multithreading concept can be used
RAM is our working memory storage. All the data, which the PC uses and works with during operation, are stored here. Data are stored on drives, typically the hard drive. However, for the CPU to work with those data, they must be read into the working memory storage, which is made up of RAM chips. To examine RAM, we need to look at the following: *RAM types (FPM, EDO, ECC, and SD RAM) * RAM modules (SIMM and DIMM) in different versions *RAM and the system bus First, let us look back in time. Not too many years ago, Bill Gates said, that with 1 MB RAM, we had a memory capacity, which would never be fully utilized. That turned out to be untrue. RAM types: The traditional RAM type is DRAM (dynamic RAM). The other type is SRAM (static RAM). SRAM continues to remember its content, while DRAM must be refreshed every few milli seconds. DRAM consists of micro capacitors, while SRAM consists of off/on switches. Therefore, SRAM can respond much faster than DRAM. SRAM can be made with a rise time as short as 4 ns. It is used in different versions in L2 cache RAM (for example pipe line Burst Cache SRAM). DRAM is by far the cheapest to build. Newer and faster DRAM types are developed continuously. Currently, there are at least four types: *FPM (Fast Page Mode) * ECC (Error Correcting Code) *EDO (Extended Data Output) * SDRAM (Synchron Data RAM) A brief explanation of DRAM types: FPM was the traditional RAM for PC's, before the EDO was introduced. It is mounted in SIMM modules of 2, 4, 8, 16, or 32 MB. Typically, it is found in 60 ns or 70 ns versions. 60 ns is the fastest and the one to use. You cannot mix different speeds on the same Pentium system board. EDO is an improvement of FPM RAM. Data are read faster. By switching from FPM to EDO, one can expect a performance improvement of 2 to 5 percent. EDO RAM are usually sold in 60 ns versions. A 50 ns version is available at higher cost. ECC RAM is a special error correcting RAM type. It is especially used in servers. SDRAM is the newest RAM type for PC's. It comes only in 64 bit modules (long 168 pin DIMM's). SDRAM has a rise time of only 8-12 ns. The performance improvement over EDO RAM is only 5 percent running at 66 MHZ, but at 100 MHZ it will prove a lot better. RAMBUS (RDRAM) is a future RAM type. Intel and others have great expectations from this type.
The address resolution protocol (ARP) is used to associate the 32 bit IP address with the 48 bit physical address, used by a host or a router to find the physical address of another host on its network by sending a ARP uery packet that includes the IP address of the receiver. The reverse address resolution protocol (RARP) allows a host to discover its Internet address when it knows only its physical address.
1. Check for cable connections 2. Check for power to the speakers 3. Check for volume control 4. Check for device drivers
The PC is built around the main, system or mother board (all meaning the same). This board is so essential for the PC, because it holds the CPU and all its connections. Let us see, what you can find on it: * ROM-chips with BIOS and other programs * CMOS, storing system setup data * The CPU * L2-cache *Chip sets with I/O controllers *RAM (Random Access Memory) mounted in SIMM or DIMM chips * Cards to connect with keyboard and mouse *Serial and parallel ports * Connectors to disk drives and EIDE drive (hard disk, CD-ROM etc.) * Slots for expansion cards * Jumpers to adjust voltage, system bus speed, clock, etc. * Contacts to reset HD activity, speaker, etc. * want to describe many of these gismos and components on the following pages.