Sector layouts Disk Hardware

Physical geometry of a disk with two zones (WD18300 has 16 zones)

A possible virtual geometry for this disk (the controller Disk parameters for the original IBM PC and does the mapping) a Western Digital WD 18300 hard disk 6/7/2001 1 6/7/2001 2

Audio CD and CD-ROM Logical data layout 600/mm 0.8micron 8-bit with bits for 5.6Km error correcting code

14*42 bits

192 bits

28% efficiency!!

Laser beam reflection can differentiate 6/7/2001 between pits and lands (1’s and 0’s). 3 6/7/2001 4

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CD-ROM characteristics CD-R (Recordable)

Single-speed= 75 sectors/sec =153.6KB/sec Blank CD with a groove having sinusoidal

40x drive = 40*153.6KB/sec ~ 6MB/sec wave form ¡

Capacity = 650MB to guide the laser beam for writing ¡ Seek time ~ several hundred milliseconds 22.05KHz to monitor rotation speed (slow) ¢ Internal layer of transparent dye that can be

Cost (blank) ~$1 burnt (to create dark spots) ¡ High power laser beam used to burn

¡ Low power laser beam used to read

¢ Incremental burning possible

¡ Kodak PhotoCD

¡ A new VTOC must be written

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Reading a CD-R CD-RW (ReWritable)

¢ Dye is replaced by an alloy with two stable states

¡ Crystalline (high reflectivity) and Amorphous (low reflectivity)

¢ Laser has 3 power levels £ ¡ High power changes C A for recording

¤ Low power is used for reading £ ¤ Medium power changes A C for erasing

¥ CD-RW blanks are more expensive than CD-R

blanks ¦ hasn’t caught on

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2 A double sided, dual layer DVD disk Digital Video Disk (DVD)

Differences from CD-ROM

¡ Has smaller pits (half as large as CD pits)

¡ Tighter spiral (twice as dense)

¡ Red laser has shorter wave length (higher resolution)

Capacity=4.7GB (7 times)

1x drive =1.4MB/sec

Can hold 133 minutes of high resolutions (720x480) video with sound tracks for 8 0.6mm languages (MPEG2) single-sided

disk Official name is Digital Versatile Disk Can store 17GB! Official name=Digital Versatile Disk

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Disk sector

16

Preamble: Special start-of-sector marker + sector number

6/7/2001 11 6/7/2001 An illustration of cylinder skew 12

3 Sector interleaving

No interleaving

Single interleaving

Double interleaving

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