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 floppy disk 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 byte 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 Disk Formatting
16 bytes
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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