Chapter 2 part 2

Computer Processing Speeds

• Milliseconds - thousands of a second

• Microseconds - millionths of a second

• Nanoseconds - billionths of a second

• Picosecond - trillionths of a second

• MIPS - millions of instructions per second

• MHz - megahertz - millions of cycles per second

Speed factors

• Size of circuit paths (system buss) that connect internal components of a microprocessor

• Processing registers

• Memory cache

• Specialized co-processors

Peripheral Devices

• Necessary for input, output, storage

• Must be linked in some manner to the cpu

• Interface technology has yielded simpler more usable devices

• Mice, touch screens, light pens, voice

• Work with graphical user interface to allow easier access

Printed Output

• Inkjet printers - spray ink on page one line at a time. Low cost, quiet, versatile.

• Laser printers - Electrostatic process similar to a photocopy. Higher cost, faster, multi- purpose

Storage Trends

• VLSI - Very large scale integration. This allows more processing power in smaller processors

• Secondary storage getting cheaper for more capacity

Computer StorageFundamentals

• Binary representation

• bit - Smallest level of a data element

• byte - a grouping of bits

• Two common types of bit arrangement– ASCII– EBCDIC

CONT.

• Storage capacities are measured in two general forms– Kilobytes - KB - one thousand bytes– Megabytes - MB - one million bytes– Gigabyte - GB - one billion bytes– Terabyte - TB - one trillion bytes

Media Access

• Two methods for accessing data or information stored on some type of media– Direct Access - Method used when the primary

storage media is semiconductor (RAM), or direct access storage device (DASD). Direct Access and Random Access can be used interchangeably

– In direct access, there is a unique identifier (address) that allows nearly immediate access

Media Access cont

• The second access method is Sequential Access – Associated with a slower retrieval of desired

information or data.– Mediums are magnetic tape, digital audio tape,

etc.– Records are stored one after the other and must

be retrieved in order of storage

Semiconductor Memory

• Benefits to semiconductor memory are numerous

• Physically small

• Fast

• Resistant to temperatures

• There is one major disadvantage to this type of memory

Semiconductor Memorycont

• Semiconductor memory only works when uninterrupted power is being supplied

• Volatility is the main concern when relying on this type of memory

• Two basic forms for Semiconductor memory

Types of SemiconductorMemory

• RAM - Random Access Memory - Most widely used primary storage medium - this is considered “Read/Write memory”

• ROM - Read Only Memory - Can be read but not erased or overwritten - there are some variations that allow contrary actions

Magnetic Disk Storage

• Floppy disks - polyester film covered with iron oxide. Contained in a hard cover. Can be erased, saved multiple times. Generally have a capacity of 1.44 megabytes

• Hard Disk drives - Sealed module containing a disk, controller, read head. Can have a large range of capacity sizes from 520megabytes to several gigabytes

Magnetic Disk Storagecont

• RAID - Redundant Array of Independent Disks - multiple hard disks that provide fault tolerance and high capacity.

Magnetic Tape

• Still used as a form of permanent storage

• Generally used as ‘back up’ for more easily accessed media

Optical Storage

• Medium that requires an electronic read eye (laser) that reads encoding on a plastic disk

• High storage capacity

• Quick access (but less than RAM)

Optical Storage types

• CD-ROM - Capable of storing 600 megabytes on a single disk. Cannot be erased or overwritten

• CD-R - Compact Disk Recordable - Allows for disks to be encoded once using a special CD-R device (drive)

• CD-RW - Compact Disk rewritable - Can be overwritten using special drive

Optical Disk cont

• DVD - Digital Video Disk - can hold 3 to 8.5 gigabytes on a single disk

• WORM - Write Once Read Many - similar to CD-R

The End

• Of chapter 2 at least………………..