1 / 18

Announcements

Announcements. Assignment #3 is up. It is due on 27 Apr. Midterm exam is back. Assignment #2 is back. Results of midterm exam are posted. Solutions to prev. assignments are posted. Lab 2 is posted. Tutorial day/time. Results of Midterm Exam. Max score: 15/15 Min score: 2/15

gavin-spears
Download Presentation

Announcements

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Announcements • Assignment #3 is up. It is due on 27 Apr. • Midterm exam is back. • Assignment #2 is back. • Results of midterm exam are posted. • Solutions to prev. assignments are posted. • Lab 2 is posted. • Tutorial day/time.

  2. Results of Midterm Exam Max score: 15/15 Min score: 2/15 Ave. score: 8/15

  3. Chapter 6. External Memory (cont.) Lecture7

  4. Optical Storage CD-ROM • Originally for audio • 650 Mbytes giving over 70 minutes audio • Polycarbonate coated with highly reflective coat, usually aluminium • Data stored as pits • Read by reflecting laser • Single spiral track. • Constant packing density • Constant linear velocity (CLV) • The disk rotates more slowly for access near the outer edge than for those near the center.

  5. CD Operation 1 0 1 Pit: rough surface, reflected laser intensity is low. Land: smooth surface, reflected laser intensity is high.

  6. CD-ROM Drive Speeds • Audio is single speed • Constant linear velocity • 1.2 ms-1 • Track (spiral) is 5.27km long • Gives 4391 seconds = 73.2 minutes • Other speeds are quoted as multiples • e.g. 24x (24*150 kByte/sec) • Quoted figure is maximum drive can achieve

  7. CD-ROM Format – One Block • Mode 0=blank data field • Mode 1=2048 byte data+error correction • Mode 2=2336 byte data

  8. Random Access on CD-ROM • Difficult • Move head to rough position • Set correct speed • Read address • Adjust to required location

  9. CD-ROM for & against • Large capacity • Easy to mass produce • Removable • Robust • Expensive for small runs • Slow • Read only

  10. Other Optical Storage • CD-Recordable (CD-R) • Now affordable • Compatible with CD-ROM drives • CD-RW • Erasable • Getting cheaper • Mostly CD-ROM drive compatible • Phase change • Material has two different reflectivities in different phase states

  11. DVD - what’s in a name? • Digital Video Disk • Used to indicate a player for movies • Only plays video disks • Digital Versatile Disk • Used to indicate a computer drive • Will read computer disks and play video disks • Officially - nothing!!!

  12. DVD - technology • Multi-layer • Very high capacity (4.7G per layer) • Full length movie on single disk • Using MPEG compression • Finally standardized • Movies carry regional coding • Players only play correct region films • Can be “fixed”

  13. DVD – Writable • Loads of trouble with standards • First generation DVD drives may not read first generation DVD-W disks • First generation DVD drives may not read CD-RW disks • Wait for it to settle down before buying!

  14. CD and DVD

  15. Magnetic Tape • Serial access • Slow • Very cheap • Backup and archive • Serial recording vs. parallel recording. • Block: record. • Interrecord gap. • Sequential access device • Magnetic disk is a direct access device.

  16. Reading Material • Stallings, chapter 6, pages: 184 - 190

More Related