1. Seagate Cheetah 15K.5, full of perpendicular goodness with 300 GB space and a mad 15,000 rpm

2. 2 Systems Architecture, Fifth Edition Chapter Goals Describe the distinguishing characteristics of primary and secondary storage Describe the devices used to implement primary storage Describe memory allocation schemes Compare and contrast secondary storage technology alternatives

3. 3 Systems Architecture, Fifth Edition Chapter Goals (continued) Describe factors that determine storage device performance Choose appropriate secondary storage technologies and devices

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5. 5 Storage Devices Consist of a read/write mechanism and a storage medium –Device controller provides interface Primary storage devices –Support immediate execution of programs Secondary storage devices –Provide long-term storage of programs and data

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7. 7 Characteristics of Storage Devices Speed Volatility Access method Portability Cost and capacity

8. 8 Systems Architecture, Fifth Edition Speed Primary storage speed –Typically faster than secondary storage speed by a factor of 105 or more –Expressed in nanoseconds (billionths of a second) Secondary storage speed –Expressed in milliseconds (thousandths of a second) Data transfer rate = 1 second/access time (in seconds) x unit of data transfer (in bytes)

9. 9 Systems Architecture, Fifth Edition Volatility Primary storage devices are generally volatile –Cannot reliably hold data for long periods Secondary storage devices are generally nonvolatile –Hold data without loss over long periods of time

10. 10 Systems Architecture, Fifth Edition Access Method Serial access (linear) Random access (direct access) Parallel access (simultaneous)

11. 11 Systems Architecture, Fifth Edition Portability Removable storage media with standardized formats (e.g., compact disc and tape storage) Typically results in slower access speeds

12. 12 Systems Architecture, Fifth Edition Cost and Capacity Cost increases: –With improved speed, volatility, or portability –As access method moves from serial to random to parallel access method Primary storage - expensive (high speed and combination of parallel/random access methods) Capacity of secondary storage devices is greater than primary storage devices

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14. 14 Systems Architecture, Fifth Edition Memory-Storage Hierarchy

15. 15 Systems Architecture, Fifth Edition Primary Storage Devices Critical performance characteristics –Access speed –Data transfer unit size Must closely match CPU speed and word size to avoid wait states

16. 16 Systems Architecture, Fifth Edition Storing Electrical Signals Directly –By devices such as batteries and capacitors –Trade off between access speed and volatility Indirectly –Uses energy to alter the state of a device; inverse process regenerates equivalent electrical signal Modern computers use memory implemented with semiconductors (RAM and NVM)

17. 17 Systems Architecture, Fifth Edition Random Access Memory Characteristics –Microchip implementation using semiconductors –Ability to read and write with equal speed –Random access to stored bytes, words, or larger data units Basic types –Static RAM (SRAM) – uses transistors –Dynamic RAM (DRAM) – uses transistors and capacitors

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19. 19 Systems Architecture, Fifth Edition Random Access Memory To bridge performance gap between memory and microprocessors –Read-ahead memory access –Synchronous read operations –On-chip memory caches

20. 20 Systems Architecture, Fifth Edition Nonvolatile Memory Random access memory with long-term or permanent data retention Usually relegated to specialized roles and secondary storage; slower write speeds and limited number of rewrites Generations of devices (ROM, Erasable Programmable ROM=EPROM, and Electronically EPROM = EEPROM)

21. 21 Systems Architecture, Fifth Edition Nonvolatile Memory Flash RAM (most common NVM) –Competitive with DRAM in capacity and read performance –Relatively slow write speed –Limited number of write cycles NVM technologies under development –Ferroelectric RAM –Polymer memory

22. 22 Systems Architecture, Fifth Edition Memory Packaging Dual in-line packages (DIPs) –Early RAM and ROM circuits Single in-line memory module (SIMM) –Standard RAM package in late 1980s Double in-line memory module (DIMM) –Newer packaging standard –A SIMM with independent electrical contacts on both sides of the module

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24. 24 Systems Architecture, Fifth Edition CPU Memory Access Critical design issues for primary storage devices and processors –Physical organization of memory –Organization of programs and data within memory –Method(s) of referencing specific memory locations

25. 25 Systems Architecture, Fifth Edition Physical Memory Organization Physical memory –Actual number of memory bytes that physically are installed in the machine Most and least significant bytes Big endian and little endian Addressable memory –Highest numbered storage byte that can be represented

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27. 27 Systems Architecture, Fifth Edition Memory Allocation and Addressing Memory allocation –Assignment of specific memory addresses to system software, application programs, and data Absolute addressing Indirect addressing (relative addressing) –Offset register

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30. 30 Systems Architecture, Fifth Edition Magnetic Storage Exploits duality of magnetism and electricity –Converts electrical signals into magnetic charges –Captures magnetic charge on a storage medium –Later regenerates electrical current from stored magnetic charge Polarity of magnetic charge represents bit values zero and one

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34. 34 Systems Architecture, Fifth Edition Magnetic Tape Ribbon of plastic with a coercible (usually metallic oxide) surface coating Mounts in a tape drive for reading and writing Relatively slow serial access Compounds magnetic leakage; wraps upon itself Susceptible to stretching, friction, temperature variations

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36. 36 Systems Architecture, Fifth Edition Magnetic Tape Two approaches to recording data –Linear recording –Helical scanning Several formats and standards (e.g., DDS [DAT], AIT, Mammoth, DLT, LTO)

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38. 38 Systems Architecture, Fifth Edition Magnetic Disk Flat, circular platter with metallic coating that is rotated beneath read/write heads Random access device; read/write head can be moved to any location on the platter Hard disks and floppy disks Cost performance leader for general-purpose on-line secondary storage

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41. 41 Systems Architecture, Fifth Edition Locating a Block of Data Average seek time: (average) time required to move from one track to another [Also called track-to-track seek time] Latency: time required for disk to rotate to beginning of correct sector [Also called rotational delay] Transfer time: time required to transfer a block of data to the disk controller buffer

42. 42 Systems Architecture, Fifth Edition Disk Access Times Avg. Seek time (track-to-track seek time) –average time to move from one track to another Avg. Latency time (rotational delay –average time to rotate to the beginning of the sector –Avg. Latency time = ½ * 1/rotational speed Transfer time –1/(# of sectors * rotational speed) Total Time to access a disk block –Avg. seek time + avg. latency time + avg. transfer time

43. 43 Systems Architecture, Fifth Edition Example Calculate the average access time for a disk rotating at 7,200 rpm, with Avg. Seek time 5 microseconds, and 500 sectors/track. SOL: Average Access Time =(seek) + (rot. Delay) + (Transfer Time) Average Access Time =(5 microseconds) + (½) * (1/7,200RPM) + 1/(500* 7,200RPM =.000005 + ½ *.0001389 (60 sec) +.000000278 (60 sec) =.000005+.004167+.0000167=.0041887sec….ANS Which performance value is the most significant?

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45. 45 Systems Architecture, Fifth Edition Disk Block Formats Single Data Block Header for Windows disk

46. 46 Systems Architecture, Fifth Edition To increase capacity per platter, disk manufacturers divide tracks into zones and vary the sectors per track in each zone.

47. 47 Systems Architecture, Fifth Edition Optical Mass Storage Devices Store bit values as variations in light reflection Higher areal density and longer data life than magnetic storage Standardized and relatively inexpensive Uses: read-only storage with low performance requirements, applications with high capacity requirements, and where portability in a standardized format is needed

48. 48 Systems Architecture, Fifth Edition Optical storage devices read data by shining laser beam on the disc.

49. 49 Systems Architecture, Fifth Edition Layout: CD-ROM vs. Standard Disk CD-ROMHard Disk

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51. 51 Systems Architecture, Fifth Edition CD-ROM Read-only; data permanently embedded in durable polycarbonate disc Bit values represented as flat areas (lands) and concave dents (pits) in the reflective layer Data recorded in single continuous track that spirals outward from center of disc Popular medium for distributing software and large data sets

52. 52 Systems Architecture, Fifth Edition CD-ROM AdvantagesDrawbacks Standardized format High density Cheap to manufacture Cannot be rewritten Capacity limited to 700 MB

53. 53 Systems Architecture, Fifth Edition CD-R Uses a laser that can be switched between high and low power and a laser-sensitive dye embedded in the disc Relatively cheap Common uses: create music CDs on home computers, back up data from other storage devices, create archives of large data sets, and manufacture small quantities of identical CDs

54. 54 Systems Architecture, Fifth Edition Phase-Change Optical Discs Enables nondestructive writing to optical storage media Materials change state easily from non-crystalline (amorphous), to crystalline, and then back again –Reflective layer is a compound of tellurium, selenium, and tin Example: CD-RW

55. 55 Systems Architecture, Fifth Edition DVD Improves on CD and CD-RW technology –Increased track and bit density: smaller wavelength lasers and more precise mechanical control –Improved error correction –Multiple recording sites and layers

56. 56 Systems Architecture, Fifth Edition Summary Storage devices and their underlying technologies Characteristics common to all storage devices Technology, strengths, and weaknesses of primary and secondary storage

57. 57 Systems Architecture, Fifth Edition Solid State Drive! In 1984, Dr. Fujio Masuoka from Toshiba invented the first flash memory, which Intel introduced as a commercial product four years later. Solid state drives based on flash memory have a number of unique advantages over conventional hard drive technology. Since they lack mechanical parts, they are much more resistant to shock, consume far less power, and release far less heat. They also produce no sound during operation and respond much more quickly than a mechanical drive. The size of a flash drive can also be very small (relative to a mechanical hard drive), resulting in a lighter device. All these advantages beg the question 'Why are we still using what might seem as an outdated mechanical hard drive technology?'

58. 58 Systems Architecture, Fifth Edition Fastest Memory (Aug 2008) The fastest memory on the market was showcased by Corsair. The company displayed the DDR3-2133MHz memory modules, which have a 1GB capacity and are capable of performing at latencies of 8-8-8-24. These “Dominator” modules are integrated with the company’s unique Dual-path Heat eXchange (DHX) technology. The DHX utilizes two paths for heat removal – an aluminum heat spreader, and a special PCB, which has a copper base that absorbs heat transferred by a dedicated heat sink. According to the company, the DHX modules, each of which includes a total of four heat sinks, provide an extremely stable, reliable, and overclockable memory. http://thefutureofthings.com/news/1143/a-look-back-at- cebit-2008-storage-and-memory.html

59. 59 Systems Architecture, Fifth Edition PCI Drive?? The DDR Drive X1 is a PCI Express based plug in card with 8GB of capacity, and bootable. According to sources close to the firm, the drive will have a custom and upgradeable high performance DMA Engine, an external power jack with a switching AC adaptor, and will go into a 512 unit initial production run. Although the firm gave no details of the pricing, a solid state drive at an affordable price is likely to be a popular item. http://www.theinquirer.net/en/inquirer/news/2006/01/03/solid-state-ddr-drive- goes-into-prototype