Group #6 External Memory

1. Group #6External Memory Manuel Franco Maria P Gil Palacios Luis Guerrero Jose Iraheta Wilder Saint - Hillarie

2. Read Mechanism • Data is retrieved from the disk via a conducting coil called the head. • The read head has a MR sensor which has an electrical resistance that depends on the direction of the magnetization of the disk under it.

3. Write Mechanism • The write also has it’s respective head, although it is possible for the sharing of read and write heads. • Exploits the fact that electricity flowing through coil produces a magnetic field. • Electric pulses are sent to the write head, and the resulting magnetic patterns are recorded on the disk below.

4. Data Organization • How it’s Done: • This is basically fitting as much data as reasonably possible on a disk. • The disk will have many tracks which are rings of space around the center. • Data are transferred to and from the disk in sectors. Each track will have hundreds of sectors. • Each adjacent track on a ring has a gap in between to avoid errors in reading each track.

5. Data Organization • Data disk layout:

6. Formatting • Prepares the disk for use. • Formatting will embed the specifications of the disk on itself so it can be read effectively. • Remember that the head won’t know where to start and end each track if it isn’t “told”.

7. Physical Characteristics • Head Motion: • Fixed Motion: • One read-write head per track • Very rare today • Movable Head: • One read-write head • Arm can be extended or retracted to position the head

8. Physical Characteristics • Disk portability: • Nonremovable Disk: • Permanently mounted in the disk drive • Example: hard disk in a personal computer • Removable Disk: • Can be removed and replaced with another one • Examples: floppy disks and ZIP cartridge disks

9. Physical Characteristics • Sides: • Double Sided: • Magnetizable coating applied to both sides • Single Sided: • Magnetizable coating only on one side • Less expensive than double sided

10. Physical Characteristics • Platters: • Single Platter: • Multiple Platters: • Stacked vertically

11. Physical Characteristics

12. Physical Characteristics • Movable head • One read-write head per platter surface • Heads have same distance from the center • Cylinder: set of all the tracks at equal distance from the center of the disk • Reduction of head movement • Increase of speed (transfer rate)

13. Physical Characteristics

14. Physical Characteristics • Head Mechanism: • Fixed gap • Read-write head has fixed distance above platter • Contact (floppy) • There is physical contact with the medium during the read or write operation • Small, flexible, and the cheapest of the disks • Winchester • Heads in sealed drive, free of contaminants • Greater data density (closer to disk’s surface)

15. Disk Performance Parameters Diagram of a disk I/O transfer

16. Disk Performance Parameters • Track selection: • Movable-head system: • Moving head • Fixed-head system: • Electronically

17. Disk Performance Parameters • Total average access time: Ta=Ts+(1/2r)+(b/rN) Where r: rotation speed b: number of bytes to be transferred N: number bytes of a track Ts: seek time

18. Disk Performance Parameters • Total average access time: Ta=Ts+(1/2r)+(b/rN) • Access time: seek time plus rotational delay • Ts: average seek time (to position head at track) • Rotational delay: time to reach the head for the beginning of the sector • Transfer time: data transfer (read or write)

19. Disk Performance Parameters • Conclusions: • Order of reading sectors is important to I/O operations. • Sequential organization is faster than random • The way of reading or writing multiple sectors can be controlled. • There can be I/O requests competing for the same disk.

20. Introduced in 1983 Low-cost disk storage technology Six optical disk systems Compact Disk

21. CD CD-ROM CD-R CD-RW DVD DVD-R DVD-RW Optical Disk Products

22. Rugged Error correction devices Composition Information retrieval Pits and lands CD-ROM

23. Inexpensive replication Removable Longer access time Not capable of being updated CD-ROM Advantages/Disadvantages

24. Prepared differently Information is recorded differently CD-R

25. Capability Method Process Advantage/disadvantage CD-RW

26. Replaced VHS analog video tape Disk space 3 major differences between CDs DVD

27. A little history about your USB Memory stick Started with something like this….

28. Trek Technology and IBM began selling the first USB flash drives commercially in 2000. IBM marketed the first such drives in North America, with its product the "DiskOnKey" (which was manufactured by the Israeli company M-Systems). HISTORYFirst commercial product

29. IBM's USB flash drive became available December 15, 2000, and had a storage capacity of 8 MB, more than five times the capacity of the commonly used floppy disks. Old 16MB IBM DiskOnKey flash drives.

30. In 2004 Trek Technology brought several lawsuits against other USB flash drive manufacturers and distributors in an attempt to assert its patent rights to the USB flash drive. A court in Singapore ordered competitors to cease selling similar productsthat would be covered by Trek's patent, but a court in the United Kingdom revoked one of Trek's patents in that country.

31. Second Generation…

32. Modern flash drives have USB 2.0 connectivity. • they do not currently use the full 480 Mb/s (60MB/s) the USB 2.0 Hi-Speed specification supports. • The fastest drives currently available use a dual channel controller

33. overall file transfer speeds vary considerably, and should be checked before purchase. • Speeds may be given in Mbyte per second, Mbit per second, or optical drive multipliers such as "180X”. • Typical fast drives claim to read at up to 30 megabytes/s (MB/s) and write at about half that.

34. USB Memory Sticks’ Types and Varieties

35. Essential components

36. There are typically four parts to a flash drive: • 1- Male type-A USB connector – provides an interface to the host computer. • 2- USB mass storage controller – implements the USB host controller. The controller contains a small microcontroller with a small amount of on-chip ROM and RAM.

37. 3- NAND flash memory chip – stores data. NAND flash is typically also used in digital cameras. • 4- Crystal oscillator – produces the device's main 12 MHz clock signal and controls the device's data output through a phase-locked loop.

39. Additional components • Jumpers and test pins. • Bunch of LEDs. • Write-protect switches. • Unpopulated space. • USB connector cover or cap. • Transport aid. • expandable storage via an internal memory card slot.

40. Size and style of packaging

41. Housing • Some manufacturers differentiate their products by using elaborate housings. • USB flash drives have been integrated into other commonly-carried items such as watches, pens, and even the Swiss Army Knife. • others have been fitted with novelty cases such as toy cars or LEGO bricks.

42. Heavy or bulky flash drive packaging can make for unreliable operation when plugged directly into a USB port; this can be relieved by a USB extension cable.

43. Examples… =D

46. USB Flash Drive • A USB flash drive consists of a NAND-type flash memory storage device integrated with a USB. • Flash memory uses the advantage of recent advances in microprocessor technology. • Memory is based on EPROM (Erasable Programmable Read-Only Memory) and EEPROM technologies. • EEPROMs were developed that broke the erasure region into smaller sections. • High-speed serial data interfaces made memory systems with serially accessed storage viable.

47. USB connector USB mass storage controller device Test points Flash Memory Chip Crystal Oscillator LED Write-Protect Switch Space for second flash memory chip USB Flash Drive

48. File System • Most flash drives ship preformatted with the FAT (File Allocation Table) or FAT 32 file system. • FAT maintenance utilities can be used. • Flash drives file system can be changed to that of the operating system. • Flash drives can be defragmented, but this brings little advantage. • Flash Drives can be partitioned.

49. Uses • Personal data transport • Application carriers • Booting operating systems • Audio players • Backup

50. Advantages • Flash drives are mechanically very robust. • Compared to hard drives, flash drives use little power. • Most modern operating systems can read and write to flash drives without installing drivers. • Flash drives are resistant to a wide range of temperatures.