COMPUTER ORGANIZATIONS CSNB123 May 2014Systems and Networking1

COMPUTER ORGANIZATIONS CSNB123 Expected Course Outcome #Course OutcomeCoverage 1Explain the concepts that underlie modern computer architecture, its evolution, functions and organization.  2Identify the best organization of a computer for achieving the best performance when asked to make a selection from the current market.  3Demonstrate the flow of an instruction cycle. 4Differentiate types of memory components in terms of its technology and usage.  5Convert integer and floating point numbers to its internal data representation. 6Construct a series of computer instructions to perform low-level processor operations. 7Explain the RISC and CISC computers, and single core and multi-core computers May2014Systems and Networking2

COMPUTER ORGANIZATIONS CSNB123 Recall: Chapter 4 – Common Memory Parameters May 2014Systems and Networking3 Memory Type TechnologySize Access Time CacheSemiconductor RAM KB 10 ns Main Memory Semiconductor RAM MB50 ns Magnetic Disk Hard DiskGigabyte10 ms,10 MB/sec Optical DiskCD-ROMGigabyte300 ms, 600 KB/sec Magnetic Tape 100s MBSec-min.,10MB/min

COMPUTER ORGANIZATIONS CSNB123 Types of External Memory Magnetic Disk Optical Magnetic Tape May 2014Systems and Networking4

COMPUTER ORGANIZATIONS CSNB123 May 2014Systems and Networking5

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk Disk  A circular platter constructed of nonmagnetic material called substrate Aluminium (old) Glass (new)  Coated with a magnetisable material May 2014Systems and Networking6

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk (Cont.) Glass  Improved surface uniformity Increases reliability  Reduction in surface defects Reduced read/write errors  Better stiffness – to reduce disk dynamics  Greater ability to withstand shock and damage May 2014Systems and Networking7

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk – Read/Write Mechanisms  Recording & retrieval via conductive coil called a head  May be single read/write head or separate ones  During read/write, head is stationary, platter rotates May 2014Systems and Networking8

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk – Read/Write (Cont.) Write Current through coil produces magnetic field Pulses sent to head Magnetic pattern recorded on surface below Read Traditional  Magnetic field moving relative to coil produces current  Coil is the same for read and write Contemporary  Separate read head, close to write head  Partially shielded magneto resistive (MR) sensor  Electrical resistance depends on direction of magnetic field  High frequency operation Higher storage density and speed May 2014Systems and Networking9

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk – Organization, Formatting & Layout TermDescription HeadA small device capable of reading from or writing to a portion of the platter rotating beneath it TrackOrganize data on the platter in a concentric set of rings WidthTrack width = head width Gapsseparate the adjacent tracks SectorsForm of transferring the data Fixed length or variable length May 2014Systems and Networking10

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk - Velocity Issue: Bit near centre of rotating disk passes fixed point slower than bit on outside of disk Solution:  Increasing the spacing between bits of information recorded in segments of the disk  The info can then be scanned at the same rate by rotating the disk at a fixed speed known as constant angular velocity (CAV) May 2014Systems and Networking11

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk - Layout Methods Diagram May 2014Systems and Networking12

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk – Constant Angular Velocity The disk is divided into a number of pie-shaped sectors and into a series of concentric tracks Advantage of CAV:  The individual blocks of data can be directly addressed by tracks and sectors Disadvantage of CAV:  The amount of data that can be stored on the long outer tracks is the only same as what can be stored on the short inner tracks May 2014Systems and Networking13

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk – Multiple Zone Recording The surface is divided into a number of concentric zones –  The number of bits per track is constant (Within the zone)  Zones farther from the center contain more bits (since more sectors) than zones closer to the center Advantage:  Increase density Disadvantage:  Require complex circuitry May 2014Systems and Networking14

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk – Physical Characteristics Head motion  Fixed head One read write head per track Heads mounted on fixed ridged arm  Movable head One read write head per side Mounted on a movable arm May 2014Systems and Networking15

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk – Physical Characteristics (Cont.) Removable disk  Can be removed from drive and replaced with another disk  Provides unlimited storage capacity  Easy data transfer between systems Non-removable disk  Permanently mounted in the drive May 2014Systems and Networking16

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk – Physical Characteristics (Cont.) Multiple Platter  One head per side  Heads are joined and aligned  Aligned tracks on each platter form cylinders  Data is striped by cylinder Reduces head movement Increases speed (transfer rate) May 2014Systems and Networking17

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk – Physical Characteristics (Cont.) Tracks and Cylinders May 2014Systems and Networking18

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk – Classifications Head mechanism #1 Traditional head  Positioned a fixed distance above the platter-allowing an air gap #2 head mechanism that actually comes into physical contact with the medium during R/W operation  Used in floppy disk 8”, 5.25”, 3.5” Small capacity Up to 1.44Mbyte (2.88M never popular) Slow Universal Cheap May 2014Systems and Networking19

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk – Classifications (Cont.) Head mechanism #3 Winchester  Aerodynamic gap  Generate or sense an electromagnetic field of sufficient magnitude - write/read  Used in sealed drive – free of contamination – able to reduce the risk of error  Operate closer to the disk’s surface  greater data density  Material - Aerodynamic foil - rests lightly on the platter’s surface May 2014Systems and Networking20

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk - Performance Depends on;  Computer system  OS  Nature of the I/O channel  Disk controller hardware May 2014Systems and Networking21

COMPUTER ORGANIZATIONS CSNB123 Magnetic Disk – Performance (Cont.) General timing of disk I/O transfer Seek time  Moving head to correct track (Rotational) latency/delay  Waiting for data to rotate under head Access time = Seek + Latency Transfer rate-the time required for the transfer data May 2014Systems and Networking22

COMPUTER ORGANIZATIONS CSNB123 May 2014Systems and Networking23

COMPUTER ORGANIZATIONS CSNB123 Optical Storage Originally for audio 650Mbytes giving over 70 minutes audio The disk is formed from a resin such as polycarbonate. Record data digitally (music/computer data) Data recorded as a series of microscopic pits on the surface of the polycarbonate May 2014Systems and Networking24

COMPUTER ORGANIZATIONS CSNB123 Optical Storage (Cont.) Organized in a single spiral track in a sequence of blocks Sectors near the outside of the disk are the same length as those near the inside Info is packed evenly across the disk in segments of the same size - scanned at the same rate by rotating the disk as a variable speed The pits are then read by the laser as a constant linear velocity (CLV) May 2014Systems and Networking25

COMPUTER ORGANIZATIONS CSNB123 Optical Storage - Writing Create a master disk – high-intensity laser Use master to make a die to stamp out copies onto polycarbonate Pitted surface - coated with a highly reflective surface (aluminium / gold) Shiny surface - protected against dust and scratches by suing a top coat of clear acrylic A label can be silkscreened onto the acrylic May 2014Systems and Networking26

COMPUTER ORGANIZATIONS CSNB123 Optical Storage - Reading Low-powered laser – retrieve information from CD Laser - shines through the clear polycarbonate Motor - spins the disk past it Intensity of the reflected light of the laser changes as it encounters a pit Lands - areas between pits A land is smooth surface which reflects back at higher intensity Change between pits and lands is detected by a photosensor -convert into a digital signal The sensor tests the surface at regular intervals The beginning or end of a pit represents a 1, when no change in elevation occur between intervals, a 0 is recorded May 2014Systems and Networking27

COMPUTER ORGANIZATIONS CSNB123 Optical Storage - Reading May 2014Systems and Networking28

COMPUTER ORGANIZATIONS CSNB123 Optical Storage – Types CD-ROM CD-R CD-RW DVD May 2014Systems and Networking29

COMPUTER ORGANIZATIONS CSNB123 Optical Storage – CD-ROM Appropriate for large amount of data Removable Disadvantages:  Read only-cannot be updated  The access time is longer compared to magnetic disk drive May 2014Systems and Networking30

COMPUTER ORGANIZATIONS CSNB123 Optical Storage – CD-R CD-Recordable Write Once Read only Memory (WORM) Compatible with CD-ROM drives May 2014Systems and Networking31

COMPUTER ORGANIZATIONS CSNB123 Optical Storage – CD-RW Erasable Getting cheaper Mostly CD-ROM drive compatible Can be rewritten and can used as secondary storage similar to magnetic disk May 2014Systems and Networking32

COMPUTER ORGANIZATIONS CSNB123 Optical Storage – DVD Digital Video Disk  Used to indicate a player for movies Only plays video disks Digital Versatile Disk  Used to indicate a computer drive Will read computer disks and play video disks May 2014Systems and Networking33

COMPUTER ORGANIZATIONS CSNB123 Optical Storage – DVD Technology Multi-layer Very high capacity (4.7G per layer) Full length movie on single disk  Using MPEG compression May 2014Systems and Networking34

COMPUTER ORGANIZATIONS CSNB123 Optical Storage – DVD (Cont.) High Definition Designed for high definition videos  Much higher capacity than DVD Shorter wavelength laser  Blue-violet range  Smaller pits HD-DVD  15GB single side single layer Blu-ray  Data layer closer to laser Tighter focus, less distortion, smaller pits  25GB on single layer  Available read only (BD-ROM), Recordable once (BR-R) and re- recordable (BR-RE) May 2014Systems and Networking35

COMPUTER ORGANIZATIONS CSNB123 May 2014Systems and Networking36

COMPUTER ORGANIZATIONS CSNB123 Magnetic Tape Tape system use the same reading/writing technique as disk system Made from polyester tape coated with magnetizable material Data on the tape are structured as a number of parallel tracks running lengthwise Serial access Slow Very cheap Backup and archive May 2014Systems and Networking37

COMPUTER ORGANIZATIONS CSNB123 Magnetic Tape (Cont.) Older version - parallel recording Have 9 tracks Store one byte at a time with additional parity bit Later system have 18 or 36 tracks Modern version - serial recording Data are laid out as a sequence of bits along each track similar to magnetic disks Data read and write in contiguous blocks called physical records on a tape Typical recording technique used in serial tapes is referred as serpentine recording May 2014Systems and Networking38

COMPUTER ORGANIZATIONS CSNB123 Additional Reference William Stallings, Computer Organization and Architecture: Designing for Performance, 8th. Edition, Prentice-Hall Inc., 2010 May2014Systems and Networking39

COMPUTER ORGANIZATIONS CSNB123 May2014Systems and Networking40 This teaching material is belongs to Systems and Networking Department College of Information Technology Universiti Tenaga Nasional (UNITEN) Malaysia 2014