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IO devices and File systems

I/o device characteristics:

Terminal.

  • One character (8 bits of data or control function) is sent at a time, one interrupt per character.
  • 10-1800 characters per second.
  • Keyboard and display are independent in most systems (no automatic echo, full duplex).
  • Usually handled with one interrupt per character, but sometimes DMA nowadays.

Raster printers.

  • Bit mapped (one bit for each dot).
  • Typically about 300 to 1200 dots per inch.
  • Impact, ink jet, or laser printing.

Tape.

  • 8mm wide by 750 feet long, or 1/2" wide by 2500 feet long..
  • Multi-track, helical, serpentine.
  • Variable length records.
  • Capacities go up to 70 GB/tape.
  • Densities of more than 30 KB/cm.
  • Inter-record gaps ofs about 10mm.
  • Transfer rates up to 5-500 MB/second.
  • Can read or write, but cannot write in middle. Can skip records.
  • Tapes are DMA devices, not one interrupt per character.

Disk.

  • Draw picture of spindle, platters, read/write-arm.
  • Typically about 1024 cylinders, 20 tracks per cylinder, 32 sectors per track, 512 bytes per sector.
  • This is a total of about 1 GB per disk, or 500,000 double-spaced typewritten pages. Typically sectors are fixed length (512-4096 bytes arepopular sizes).
  • Sectors can be read and written individually, or in adjacent groups.
  • Seek time = 5-100 ms, latency is 0-15 ms (drive spins at 3600- 7200 RPM). This is the standard for medium term computer storage. Transfer timesare about 5-20 MB/second. These times depend on drive, controller, and interface standard (IDE, SCSI).

Cd-roms.

  • Current CD-ROMS's can hold up to 720 MB (650 MB is more typical) of data or 74 minutes of uncompressed audio. The data is organized in one (or afew) continuous spirals. The block size is 2K and "tracks" vary in size from 8 to 23 blocks There is extensive error correction information encoded with thedata.
  • Seek time = 100-300 ms. Transfer times are about .3-1.5 MB/second (for 2X-10X). 1X (150 KB/second) is needed for audio CD's.
  • Next generation CD (DVD) should store about 5-10 GB and be fully readable and writable. These drives will handle fully integrated data, audio,and video. There are currently several competing standards (ala the VHS vs. Beta competition of the 80's).

Disks and tapes read and write blocks of information rather than single bytes:

  • Storage efficiency: give example for tape. At 1600 bpi, 80-byte records use .05 inch, gaps use .6 inch, tape is all gap. However, 8000-byterecords use 5 inches so gaps are only about 11% of the tape. In the case of disks, there are a couple of thousand bits of leader at the beginning of eachsector used to identify the sector and to synchronize when reading. For 1000- byte sectors, 20% of the disk space is wasted.
  • Access efficiency: on disk it typically takes 25ms overhead before transfer begins. The actual transfer is only about 1 microsecond perbyte. Thus one-byte transfers take 25ms total time/byte, 1000-byte transfers take about 25 ms total time/byte. Re-iterate the importance of eliminatingseeks.

Two common I/O device access methods: DMA and CPU control

Questions & Answers

physiological Psychology
Nwosu Reply
How can I develope my cognitive domain
Amanyire Reply
why is communication effective
Dakolo Reply
Communication is effective because it allows individuals to share ideas, thoughts, and information with others.
effective communication can lead to improved outcomes in various settings, including personal relationships, business environments, and educational settings. By communicating effectively, individuals can negotiate effectively, solve problems collaboratively, and work towards common goals.
it starts up serve and return practice/assessments.it helps find voice talking therapy also assessments through relaxed conversation.
miss
Every time someone flushes a toilet in the apartment building, the person begins to jumb back automatically after hearing the flush, before the water temperature changes. Identify the types of learning, if it is classical conditioning identify the NS, UCS, CS and CR. If it is operant conditioning, identify the type of consequence positive reinforcement, negative reinforcement or punishment
Wekolamo Reply
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Wekolamo
because it helps many people around the world to understand how to interact with other people and understand them well, for example at work (job).
Manix Reply
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ARC
A child is a member of community not society elucidate ?
JESSY Reply
Isn't practices worldwide, be it psychology, be it science. isn't much just a false belief of control over something the mind cannot truly comprehend?
Simon Reply
compare and contrast skinner's perspective on personality development on freud
namakula Reply
Skinner skipped the whole unconscious phenomenon and rather emphasized on classical conditioning
war
explain how nature and nurture affect the development and later the productivity of an individual.
Amesalu Reply
nature is an hereditary factor while nurture is an environmental factor which constitute an individual personality. so if an individual's parent has a deviant behavior and was also brought up in an deviant environment, observation of the behavior and the inborn trait we make the individual deviant.
Samuel
I am taking this course because I am hoping that I could somehow learn more about my chosen field of interest and due to the fact that being a PsyD really ignites my passion as an individual the more I hope to learn about developing and literally explore the complexity of my critical thinking skills
Zyryn Reply
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Jonathan
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Jonathan
generally amnesi how long yrs memory loss
Kelu Reply
interpersonal relationships
Abdulfatai Reply
What would be the best educational aid(s) for gifted kids/savants?
Heidi Reply
treat them normal, if they want help then give them. that will make everyone happy
Saurabh
What are the treatment for autism?
Magret Reply
hello. autism is a umbrella term. autistic kids have different disorder overlapping. for example. a kid may show symptoms of ADHD and also learning disabilities. before treatment please make sure the kid doesn't have physical disabilities like hearing..vision..speech problem. sometimes these
Jharna
continue.. sometimes due to these physical problems..the diagnosis may be misdiagnosed. treatment for autism. well it depends on the severity. since autistic kids have problems in communicating and adopting to the environment.. it's best to expose the child in situations where the child
Jharna
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Jharna
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Jharna
what is learning? discuss how any three scholars propounded on how learning is
Grace Reply
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Source:  OpenStax, Operating systems. OpenStax CNX. Aug 13, 2009 Download for free at http://cnx.org/content/col10785/1.2
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