Software Complexity Creation - Research Study | CMSC 412, Study notes of Operating Systems

Material Type: Notes; Professor: Hollingsworth; Class: Operating Systems; Subject: Computer Science; University: University of Maryland; Term: Unknown 1989;

Typology: Study notes

Pre 2010

Uploaded on 02/13/2009

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CMSC 412 –S02 (lect2)
Announcements
Program #0
its due Monday
See note on web page about running bochs on wam
Keyboard driver will produce events for key down and up
See keyboard.h for how to tell which is which
Only echo for one
Cell Phones and Pagers
Must be to “off” or “vibrate” during class
Failure to comply will lower your grade in the class
Reading
Chapter 2
Chapter 3 (for Tuesday)
pf3
pf4
pf5
pf8
pf9
pfa

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  • S02 (lect 2)

Announcements

l^

Program #0^ – its due Monday– See note on web page about running bochs on wam– Keyboard driver will produce events for key down and up

  • See keyboard.h for how to tell which is which• Only echo for one

l^

Cell Phones and Pagers^ – Must be to “off” or “vibrate” during class– Failure to comply will lower your grade in the class

l^

Reading^ – Chapter 2– Chapter 3 (for Tuesday)

  • S02 (lect 2)

Software Complexity Creation

Research Study

l^

Researcher: Prof. David P. Darcy & Meng Ma

l^

Task: a C++ Programming task

l^

Payoff: $50 for 4-5 hours

l^

Time: Saturday, Feb 2

nd

at 10am

l^

More details can be found at:

http://wam.umd.edu/~meng/participation.html

  • S02 (lect 2)

I/O Systems

l^

Many different types of devices^ – disks– networks– displays– mouse– keyboard– tapes

l^

Each have a different expectation for performance^ – bandwidth

  • rate at which data can be moved
    • latency
      • time from request to first data back

Different Requirements lead to Multiple – S02 (lect 2)

Buses

l^

Processor Bus (on chip)^ – Many Gigabytes/sec

l^

Memory Bus (on processor board)^ – ~1-2 Gigabyte per second

l^

I/O Bus (PCI, MCA)^ – ~100 megabytes per second– buses are more complex than we saw in class

  • show PCI spec.

l^

Device Bus (SCSI, USB)^ – tens of megabytes per second

  • S02 (lect 2)

Disks

l^

Several types:^ – Hard Disks - rigid surface with magnetic coating– Floppy disks - flexible surface with magnetic coating– Optical (CDs and DVDs) - read only, write once, multi-write

l^

Hard Disk Drives:^ – collection of platters– platters contain concentric rings called tracks– tracks are divided into fixed sized units called sectors– a cylinder is a collection of all tracks equal distant from the

center of disk

  • Current Performance:
    • capacity: megabytes to hundreds of gigabytes• throughput: sustained < 10 megabytes/sec• latency: mili-seconds
  • S02 (lect 2)

I/O Interfaces

l^

Need to adapt Devices to CPU speeds

l^

Moving the data^ – Programmed I/O

  • Special instructions for I/O
    • Mapped I/O
      • looks like memory only slower
        • DMA (direct memory access)
          • device controller can write to memory• processor is not required to be involved• can grab bus bandwidth which can slow the processor down
  • S02 (lect 2)

I/O Operations

l^

Synchronous I/O^ – program traps into the OS– request is made to the device– processor waits for the device– request is completed– processor returns to application process

l^

Asynchronous I/O^ – request is made to the device– processor records request– processor continues program

  • could be a different one
    • request is completed and device interrupts– processor records that request is done– program execution continues
  • S02 (lect 2)

Hardware Protection

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Need to protect programs from each other

l^

Processor has modes^ – user mode and supervisor (monitor, privileged)– operations permitted in user mode are a subset of supervisor

mode

l^

Memory Protection^ – control access to memory– only part of the memory is available

  • can be done with base/bound registers

l^

I/O Protection^ – I/O devices can only be accessed in supervisor mode

l^

Processor Protection^ – Periodic timer returns processor to supervisor mode