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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
A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what are the types of wave
Maurice
fine, how about you?
Mohammed
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
Who can show me the full solution in this problem?
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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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