Relatively New RAM-RDRAM

• RDRAM---Rambus RAM • It is a very fast different type of DRAM.• Rambus is the company’s name. Intel has adopted

this RAM for a while. • The special RDRAM bus delivers address and

control information using an asynchronous block-oriented protocol.

• The bus can address up to 320 RDRAM chips and it rated at 1.6 GBps

External Memory

• 1. Magnetic disk---Floppy disk, hard disk

• 2. Magnetic tape

• 3. Optical Memory---CD, CD-R, CD-RW…

• DVD, DVD-RW.

Registers

Cache

Main Memory

Magnetic disk

Tape Optical disk

7

• This storage organization can be thought of as a pyramid:

S N

S N

S N

S N

0.1-0.2 microns

1 bit

5-10 microns

1-track width

shield

MR sensorWrite head

Magnetic disk (HD)

IwIr

MR---Magnetoresistive Sensor

• The MR material has an electrical resistance that depends on the direction of the magnetization of the medium moving under it.

• By passing a current through the MR sensor, resistance changes are detected as voltage signals.

• Main advantage: High frequency operation-----High Speed.

HD-related terms

• Track

• Sector

• Cylinder

• Spindle speed RPM

• Capacity

• Track-to Track Seek Time

• Average Seek Time

Disk tracks are numbered from the outside edge, starting with zero.

• Hard disk platters are mounted on spindles.

• Read/write heads are mounted on a comb that swings radially to read the disk.

• The rotating disk forms a logical cylinder beneath the read/write heads.

• Data blocks are addressed by their cylinder, surface, and sector.

HD --- cont…,

• Average Rotational Delay

• Maximum Transfer Rate

• Bytes per Sector

• Sector per Track

• Track per Cylinder

• Constant Angular Velocity

Transfer Time

• T = b/rN Where

• T = transfer time

• b = number of bytes to be transferred

• N = number of bytes on a track

• r = rotation speed, in revolution per second

• There are a number of electromechanical properties of hard disk drives that determine how fast its data can be accessed.

• Seek time is the time that it takes for a disk arm to move into position over the desired cylinder.

• Rotational delay is the time that it takes for the desired sector to move into position beneath the read/write head.

• Seek time + rotational delay = access time.

• Transfer rate gives us the rate at which data can be read from the disk.

• Average latency is a function of the rotational speed:

• Mean Time To Failure (MTTF) is a statistically-determined value often calculated experimentally.– It usually doesn’t tell us much about the actual expected

life of the disk. Design life is usually more realistic.

Figure 7.11 in the text shows a sample disk specification.

• Floppy (flexible) disks are organized in the same way as hard disks, with concentric tracks that are divided into sectors.

• Physical and logical limitations restrict floppies to much lower densities than hard disks.

• A major logical limitation of the DOS/Windows floppy diskette is the organization of its file allocation table (FAT). – The FAT gives the status of each sector on the disk:

Free, in use, damaged, reserved, etc.

• On a standard 1.44MB floppy, the FAT is limited to nine 512-byte sectors. – There are two copies of the FAT.

• There are 18 sectors per track and 80 tracks on each surface of a floppy, for a total of 2880 sectors on the disk. So each FAT entry needs at least 14 bits (214=4096 < 213 = 2048).– FAT entries are actually 16 bits, and the organization is

called FAT16.

• The disk directory associates logical file names with physical disk locations.

• Directories contain a file name and the file’s first FAT entry.

• If the file spans more than one sector (or cluster), the FAT contains a pointer to the next cluster (and FAT entry) for the file.

• The FAT is read like a linked list until the <EOF> entry is found.

• A directory entry says that a file we want to read starts at sector 121 in the FAT fragment shown below.

– Sectors 121, 124, 126, and 122 are read. After each sector is read, its FAT entry is to find the next sector occupied by the file.

– At the FAT entry for sector 122, we find the end-of-file marker <EOF>.

IDE---versus---SCSI

• IDE---Integrated Drive Electronics

• It has a limit of drive size of 528 MB

• Due to the BIOS calling convention

• 4 bits for head, 6 bits for the sector, 10 bits for the cylinder. The max. drive then has 16 heads, 63 sectors and 1024 cylinders

• ----which lead to the 528MB

• EIDE--- Extended IDE

SCSI (Small Computer System Interface)Disks

• Main features:

• 1. Faster

• 2. Allows more active drives at the same time 7 devices for SCSI and 15 devices for wide SCSI for a single SCSI Controller.

RAID---Redundant Array of Inexpensive Disks

(Independent Disks in other textbook)

• Purpose---Increase both speed and reliability

• Total 7 (0-6) levels in RAID scheme.

• All the 7-levels share three common characteristics:

• 1. RAID is a set of physical disk drives viewed by the operating system as a single logical drive.

• 2. Data are distributed across the physical drives of an array.

• 3. Redundant disk capacity is used to store parity information, while guarantees data recoverability in case of a disk failure.

These levels do not imply a hierarchical relationship

• Level 0 doesn’t support the third characteristics.

• Level 2 and 4 are not commercially offered and are not likely to achieve industry standard.

RAID Level 0 (nonredundant)

• Level 0 scheme

Strip 12

Strip 8

Strip 4

Strip 0

Strip 13

Strip 9

Strip 5

Strip 1

Stri14

Strip 10

Strip 6

Strip 2 Strip 3

Strip 7

Strip 11

Strip 15

Level 1---Mirrored

• In this level, it added another same set of disks

• main feature:

• 1. Increased reliability.

• 2. Same write speed.

• 3. Double read speed can be realized.

• 4. Easy to replace a bad disk.

• .

Strip 12

Strip 8

Strip 4

Strip 0

Strip 13

Strip 9

Strip 5

Strip 1

Stri14

Strip 10

Strip 6

Strip 2 Strip 3

Strip 7

Strip 11

Strip 15

Array management

software

Strip 0Strip1Strip2Strip 3

Logical disk

RAID….

• The main feature is the speed and reliability.

• Due to the reason of cost, RAID is mainly used on larger systems.

Serial and parallel ATA HD– Right now, the ATA hard drive landscape looks

pretty good, and it's about to get even better.– Current ATA hard drives use the ATA/100 and

ATA/133 specs, which are limited to transfer rates of 100 and 133MB/sec, respectively.

– These drives use bulky 80-pin ribbon cables that clutter case interiors and interfere with internal air flow, but help is on the way.

– The new Serial ATA standard promises transfer rates of up to 150MB/sec using thin, flexible cables might make some wonder how they got by with IDE ribbons at all.

ATA -- Examples

• Maximum Signaling Devices per Pins per • transfer rate voltage channel channel• (MB/sec) (volts)

• ATA/133 • 133 5 2 40

• Serial ATA

• 150 0.25 1 7

The main difference between the two

• Though Serial ATA offers a higher peak transfer rate performance than the fastest parallel ATA standard.

• Serial ATA's signaling voltage is just 0.25V, one twentieth that of parallel ATA.

• Such a low signaling voltage makes Serial ATA an attractive technology for mobile devices, but I can't imagine that the average desktop user will see much benefit from Serial ATA's lower power consumption.

• Corporate IT types may appreciate Serial ATA's potential for lower power consumption for multi-drive RAID arrays that are constantly active.

What is ATA?• ATA Short for Advanced Technology

Attachment.

• a disk drive implementation that integrates the controller on the disk drive itself.

• There are several versions of ATA, all developed by the Small Form Factor (SFF)

Committee:

ATA

• ATA: Known also as IDE, supports one or two hard drives, a 16-bit interface and PIO modes 0, 1 and 2.

• ATA-2: Supports faster PIO modes (3 and 4) and multiword DMA modes (1 and 2). Also supports logical block addressing (LBA) and block transfers. ATA-2 is marketed as Fast ATA and Enhanced IDE (EIDE).

• ATA-3: Minor revision to ATA-2.

ATA• Ultra-ATA: Also called Ultra-DMA, ATA-33, and

DMA-33, supports multiword DMA mode 3 running at 33 MBps.

• ATA/66: A version of ATA proposed by Quantum Corporation, and supported by Intel, that doubles ATA's throughput to 66 MBps.

• ATA/100: An updated version of ATA/66 that increases data transfer rates to 100 MBps.

• ATA also is called Parallel ATA. Contrast with Serial ATA.

Serial ATA

• http://www.explosivelabs.com/articles/sata/

CD• . 12mm

120mm in diameter

1.2mm thickness

CD –ROMs

• Working principle: LabelProtective acrylic

Polycarbonate plastic Aluminum or othermetalsLaser beams

LandPit

Cross Section of CD-R

• .

Polycarbonate Substrate

Printed labelProtective lacquerReflective gold layer

1.2mm

Dye layer

Transmit beam

Reflective beam

Dark spot burned by laser

Information on the CD disks

• Data are written in series form and are read in series fashion, too.

• The disks have to rotate with a constant linear velocity for CD-music.

• Single-speed CD-ROM drives operate at 75sectors/sec---153,600 bytes/sec in mode 1 and 175,200 bytes/sec in mode 2.

• The difference between 1 and 2 is between music and video mode or data mode.

Yellow Book Definition

• The basic format of a CD-ROM consists of encoding every byte in a 14 –bit symbol.

• A group of 42 consecutive symbols forms a 588-bit frame. (each frame holds 192 data bits and the remaining 396 bits are used for error correction and control)

• 98 frames make 1 sector

Similarity to HD

• Both are external memories

• Both disks rotate and have the head move above the disks

• The heads float on the surface of the disks

• Both can be made with high capacity

The Differences Between the Two

• HD is much faster than CD-ROM or CD-RW

• CD-ROMs have much longer life if handled carefully.

DVD

• The capacity improvement are due to 3 factors:

• 1. Smaller pits (0.4 microns versus 0.8 )

• 2. A tighter spiral (0.74 microns versus 1.6)

• 3. A red laser at 0.65 microns versus 0.78 microns.

Capacity of DVD

• 1. Single-sided, single-layer (4.7GB).

• 2. Single-sided, dual-layer (8.5GB).

• 3. Double-sided, single-layer (9.4GB).

• 4. Double-sided, dual-layer (17GB).

Newer Blue-Laser DVD• There is a war between two new DVD

standard right now.

• One is SONY’s blue-ray system and the other is Toshiba’s HD-DVD system.

• Nov 11, 2004 - Sharp Introduces Blu-ray Disc Recorder with Hard Drive/DVD

Blue-Ray • Sharp today announced that they

will introduce a new Blu-ray Disc recorder on the Japanese market in December. (11/11/2004)

• The new BD-HD100, which features a built-in hard drive (160GB), can record and play back high-definition video (HDTV) without any loss in quality.

• It comes equipped with the world's first twin BD/DVD tray that enables

Blue-Ray• digital dubbing between the hard drive,

DVDs, and Blu-ray Discs, including the ability to dub five DVDs (4.7GB) onto a single Blu-ray Disc (25GB).

• The recorder also features an HDMI output jack, enabling users to enjoy full-digital high-definition video and high-fidelity audio with no signal deterioration by outputting recorded high-definition video (HDTV) to a compatible monitor for playback.

• The BD-HD100 will begin selling in Japan next month for about 320,000 yen ($2,991).

Blue-Ray

• http://www.blu-ray.com/

Key-Component – Blue Laser• Blu-ray uses a blue laser to record data

on discs, while CD and DVD systems use red lasers.

• Blue lasers have a shorter wavelength--405 nanometers compared to around 650 nanometers on DVD systems.

• --and that means the laser beam can be focused onto a smaller area of the disc surface.

• In turn, this means less area is needed to store one bit of data and so more data can be stored on a disc.

Blue-Ray

• The format is backed by Sony, Hitachi, LG Electronics, Matsushita Electric Industrial (Panasonic), Philips Electronics, Pioneer Electronics, Samsung Electronics, Sharp, and Thomson Multimedia.

HD-DVD

• First Blood in the New DVD War

The Toshiba-backed high-definition format may soon get support from

three major Hollywood studios.

• That could put Sony's team in a tight spot

What this war means to us?

• Like the old war between Bata standard and VHS standard, consumers will be the victim along with the loser of the two, because the industry world normally have to pick one as the winner.

• What do we buy now?

• Nobody knows!

• Fortunately, both will support your current 4.7GB DVD disks.

MRAM -- Magnetic Ram

• Infineon, IBM show prototype 16Mb magnetic RAM

• Prototype MRAM chip brings power-saving technology one step closer

MRAM

• MRAM is expected to first be used in mobile applications as a replacement for flash.

• At some point in the future, MRAM could also replace SRAM and DRAM, which is cheap to manufacture but is slower than MRAM and requires a constant power supply to retain stored data.

• Using MRAM instead of DRAM in notebooks PCs could help extend battery life, according to Infineon and IBM.