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Title: magnetism-data addressing


1
MAGNETIC DATA STORAGE AND RECORDING
DATA ADDRESSING
BY, A. POOJA SHUKLA M.Tech (NANO)
Ist Yr 1821310006 SRM UNIVERSITY
2
DATA ADDRESSING
  • A data or information found in a particular
    address
  • A data can be randomly selected or easy to find
    in the given array with the help of the given
    address
  • Types of data addressing,
  • CHS
  • ECHS
  • LBA

3
ADVANTAGES
  • Write Protection
  • Erasing
  • Security
  • Removable media
  • Removable device
  • Managing

4
BIOS
5
  • Basic Input Output System.
  • Is a set of initial code to run your PC.
  • Intel have designed their CPUs always to begin
    execution of code at address FFFF0.
  • The first instruction is a jump instruction to
    the main part of BIOS code which could be
    "anywhere" else
  • As well as testing and initializing the hardware
    in the Power On Self Test (POST)

6
  • For the purpose of booting up the computer, the
    BIOS is used for three main functions
  • Providing a set of assembler subroutines that can
    be called by the operating system and whose
    function is to access the hardware components of
    the computer such as hard disk.
  • Initiates Power On Self Test (POST).
  • Allowing changes to the low level setup options.
  • Initiating the boot sequence after a hardware
    Reset.

7
ATA
8
A set of standards called the ATA
(AT-Attachment) came into being in 1989 that
effectively put a boundary on what was possible
in terms of cylinder, head and sector numbers.
9
  • ATA-5 says (amongst other things) that
  • The cylinder number must be represented by 16
    binary digits.
  • The head number must be represented by 4 binary
    digits.
  • The sector number must be represented by 8 binary
    digits.
  • A total of 28 bits.

10
CYLINDER HEAD SECTOR (CHS)
11
  • CHS, Method for giving addresses to each
    physical block of data on a hard disk drive
  • It can be low level formatted to different
    capacities

12
  • Identifying individual sectors on a disk by
    their position in a track
  • The track is determined by the head and cylinder
    number
  • For addressing the sector in smallest unit

13
Hard Disk Geometry
  • Description Terminology
  • Heads on a Platter Head
  • A stack of Rings or "Tracks" Cylinder
  • Segment Sector

14
Where the data is physically on the disk?
  • disk controller allows us to specify only the
    Cylinder, Head and Sector that we want to access
  • The disk controller calculates where the data is
    physically on the disk and hands the data back to
    us
  • More accurately CHS is a pointer in memory to the
    data.

15
How the physical disk is accessed
  • If we wanted to access one particular sector, we
    could reference it by specifying
  • C which head it was on,
  • H which cylinder it was on and finally
  • S which sector it was on.
  • That would then uniquely identify the sector that
    we wanted to access.

16
CHS Values
  • 16-bit Cylinder value (C)
  • 4-bit Head Value (H)
  • 8-bit Sector Value (S)
  • Old BIOS
  • 10-bit C
  • 8-bit H
  • 6-bit S
  • Limited to 528MB disk

17
LOGICAL BLOCK ADDRESSING (LBA)
18
  • Used for specifying the location of blocks of
    data stored
  • Generally in secondary storage system eg, hard
    disks
  • It is an simple linear addressing scheme
  • Blocks are arranged by an integer index
  • example LBA 0, LBA 1

19
  • The five most important things to note about LBA
    are
  • LBA is a translation method based on the CHS
    addressing scheme
  • LBA was not (as many web sites claim) invented to
    overcome any disk size limits
  • It is simply a different way of accessing the
    hard disk
  • LBA does not require the BIOS to know anything
    about the disk geometry to access the disk
  • LBA is used to address data

20
EXTENDED CHS (ECHS)
21
  • It is also called as large mode CHS
  • It uses BIOS translation method
  • It is inherited by CHS mode to be in given size
    barrier (504 MB)

22
  • The BIOS coders agreed on a way round the 504 MB
    limitation. They came up with a system called
    Enhanced CHS, or ECHS.
  • ECHS is a simple translation method written on
    the end of the interrupt INT13h.
  • In summary, this is what happens
  • O/S --gt INT13h --gt ECHS Translation --gt CHS call
    --gt Disk Controller

23
  • Consequently, the requirements for this type of
    disk access are as follows
  • An operating system that can make INT13h calls.
  • A BIOS that understands INT13h calls.
  • A BIOS that can perform the ECHS translations.
  • A BIOS that can make CHS calls.
  • A disk controller that understands the
    (translated) CHS values referenced.

24
Storage Characteristics
  • Volatility
  • Non-Volatile
  • Volatile
  • Mutability
  • Read/Write
  • Read Only
  • Slow Write, Fast Read Storage
  • Accessibility
  • Random Access
  • Sequential Access
  • Addressability
  • Location
  • File
  • Content

25
THANK YOU!!
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