Computer Hardware Part 2

Microprocessors popular microprocessors AMD and Intel are comparable AMD (Advanced Micro Devices) Motorola AMD and Intel are comparable Pentium 4 Itanium Celeron Athlon Duron The microprocessor that’s best for you depends upon your budget and the type of work and play you plan to do 4/7/2019 M. Eyadat

Random Access Memory RAM (random access memory) - an area of the computer that temporarily holds data before and after it is processed as you type, characters are held in RAM It holds the data and the instructions for processing the data It even houses OS instructions 4/7/2019 M. Eyadat

Random Access Memory RAM is primary storage (main memory) Measured in megabytes (MB) Today’s computers have between 64 and 512 megabytes of RAM Amount of RAM depends on software you use You can purchase additional RAM A computer can use disk storage to simulate RAM. This is called virtual memory Not as fast as RAM 4/7/2019 M. Eyadat

RAM components vary in speed, technology, and configuration Speed is measured in nanoseconds. 1 nanosecond is 1 billionth of a second It can also be expressed in MHz (millions of cycles per second) Most computers use SDRAM (synchronous dynamic RAM) Another type is RDRAM (Rambus dynamic RAM) 4/7/2019 M. Eyadat

RAM & Disk Storage Capacitors are microscopic electronic parts that hold the electronic signals for the code that represents data. charged capacitor = ON discharged capacitor = OFF each bank of capacitors holds eight bits Disk storage is fairly permanent Floppy disks, hard disks, or CDs 4/7/2019 M. Eyadat

Read-Only Memory ROM (read-only memory) is one or more chips containing instructions that help a computer prepare to process tasks ROM is permanent and non-volatile Only way to change the instructions on a ROM chip is to replace the chip 4/7/2019 M. Eyadat

Read-Only Memory Since RAM is empty when a computer is turned on, ROM BIOS is used ROM BIOS (basic input/output system) is a set of instructions that tells computer how to access the disk drives and peripheral devices Once operating system is loaded, the computer can understand your input, run software and access your data 4/7/2019 M. Eyadat

CMOS memory A computer needs a semi-permanent way of keeping boot data, such as the number of hard disk sectors and cylinders CMOS memory - holds data but requires very little power to retain its contents Retains important computer settings after you turn the power off can run by a battery on the motherboard housed within the same chip carrier as ROM BIOS Some computers have plug and play feature for updating CMOS 4/7/2019 M. Eyadat

Storage Devices A storage device, such as a floppy disk drive, a hard drive, zip drive, and a CD-ROM drive, is used to store the data A storage medium is the disk, tape, CD, DVD, paper or other substance that contains data Storing Data Retrieving Data 4/7/2019 M. Eyadat

Storage Technologies Magnetic storage It stores data by magnetizing microscopic particles on the disk or tape surface Read-write head - mechanism in the disk drive that reads and writes magnetized particles that represent data Data stored on magnetic media such as floppy disks can be altered by dust, smoke, heat, and mechanical problems. Some experts estimate that the reliable life span of data stored on magnetic media is about three years 4/7/2019 M. Eyadat

Storage Technologies Optical storage It stores data as microscopic light spots (lands) and dark spots (pits) on the disk surface Data stored on an optical storage device is less susceptible to environmental damage 4/7/2019 M. Eyadat

Which storage technology is best? Versatility can access data from different media Durability less susceptible to damage Storage capacity - maximum amount of data that can be stored on a storage medium 4/7/2019 M. Eyadat

Which storage technology is best? Speed - measured by access time and data transfer rate Access time - average time it takes a computer to locate data and read it millisecond = one-thousandth of a second Random access - ability of a device to jump directly to the track or sector holding the data floppy disk, hard drive, CD, DVD, zip disks 4/7/2019 M. Eyadat

Floppy disk Technology A floppy disk is a round piece of flexible mylar plastic covered with a thin layer of magnetic oxide and sealed inside a protective casing 3 ½ diskettes have capacity of 1.44 MB Other floppy disk types ZIP disks – 100 MB and 250 MB Superdisks – 120 MB Disk density - closeness and size of magnetic particles it stores Zip disks and Superdisks store data at a higher density than a standard 3 ½ floppy disk Major advantage – portability Major disadvantage – not a particularly speedy device and limited storage capacity 4/7/2019 M. Eyadat

Hard Disk Technology It provides lots of storage capacity It provides faster access to files than floppy disk drives It is economical Hard disk platter - a flat, rigid disk made of aluminum or glass and coated with magnetic oxide density far exceeds floppy disk Hard disk - one or more platters and their associated read-write heads. preferred type of main storage A hard drive mechanism includes a circuit board called a controller that positions the disk and read-write heads to locate data 4/7/2019 M. Eyadat

Hard Disk Technology Removable hard disk - hard disks that can be inserted and removed from drive increase storage capacity provides security for data RAID - (redundant array of independent disks) type of hard disk storage found on mainframe and microcomputer installations contains many disk platters provides redundancy faster data access 4/7/2019 M. Eyadat

Tape Storage Tape most popular form of storage in 1960s Recent revival in tape storage for backing up data, not for principal storage device. Tape backup - copy of data on hard disk stored on magnetic tape. Requires sequential access Inconvenient and slow Data is arranged as essentially a long sequence of bits that begin at one end of the tape and stretches to the other Tape drives are available in either internal or external models 4/7/2019 M. Eyadat

CD Technology CD-ROM stands for Compact Disc Read-Only Memory data stamped on when manufactured coated with clear plastic, durable estimated life exceeds 500 years inexpensive to manufacture ideal for distribution of large files A single CD-ROM holds up to 650 MB It is very durable Original CD-ROM had speeds of 150 KB per second Today, speeds of 24x or higher (24 x 150 KB per second) 4/7/2019 M. Eyadat

DVD Technology DVD (digital video disc or digital versatile disc) variation of CD technology designed to provide enough storage capacity for a full length movie will replace video tape (experts believe) DVD-ROM disk (sometimes used for DVD-Video) stamped with data when manufactured cannot change or add data stores 4.7 GB ideal for games, maps, large databases 4/7/2019 M. Eyadat

Input/Output Devices Data Bus carries data from one component to another I/O (computer jargon for input/output) refers to collecting data and transporting results. Expansion bus - the segment of the data bus that transports data between RAM and peripheral devices 4/7/2019 M. Eyadat

Input/Output Devices Peripheral Devices Display devices Printers 4/7/2019 M. Eyadat