IOclassroomslides

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I/O-classroom-slides
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Computer
Device Controller
Input/Output Device
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Memory mapped I/O
CPU
Address
Data
0
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Main memory
Data register (address 5000)
0
7
Ready
IF
IE

Status register (address 5002)
Keyboard controller
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Processor
DMA
Memory
C
Processor to Controller Move N bytes from disk
location X to memory location M
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DMA
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DMA Transfer example
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PCI bus with System Bus
CPU
System bus
Bridge
Memory
PCI bus
Controller
Controller
Controller
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I/O Processor
CPU
I/O processor
System bus
Bridge
I/O bus
Shared Memory
Controller
Controller
Controller
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Typical Seagate Barracuda-8 7200 RPM Seek
8 ms Rot lat 4 ms Platter size 133 GB
Tot cap 400 GB Xfer rate 150 MB/sec
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• Example 1
• Suppose a disk drive has 256 bytes per sector,
  12 sectors per track, 100 tracks per surface and
  6 platters. What is the total capacity of such a
  drive in bytes?

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• Example 2
• Assuming the disk drive from Example 1, what
  would be the time to read 6 sectors from the same
  track versus 6 sectors at random assuming average
  seek time is 20 ms and a rotational speed of 3600
  RPM.

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Introduced in early 60s
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Early 60s capacity per removable pack 7.25 MB
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4 GB drive
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Recording surface On both sides
Outer tracks more sectors
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FCFS
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SSTF
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SCAN
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C-SCAN
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FCFS
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SSTF
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SCAN
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C-Scan
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C-Look