'
`
`'- Vol. 3, No. 3
`$2.95 in USA
`-.:.adat£2.10 in U.K.
`-.
`‘ Publication
`
`.-
`
`MASS STORAGE
`
`Apple Exhibit 4409
`Apple v. SightSound Technologies
`CBM2013-00023
`
`Page 00001
`
`Apple Exhibit 4409
`Apple v. SightSound Technologies
`CBM2013-00023
`Page 00001
`
`

`

`HUI!
`
`Volume 8. Number 3
`
`Features
`
`March 1983
`
`33 'I A Peek into the IBM PC by Tim Field r An
`assembly-language program enables an EpSon printer to
`display all 256 characters used by the IBM PC.
`389 Keywords In a Fuzzy Context by Thomas A.
`Smith l' CBASlC programs for bibliographic search tell you
`the degree to which various articles meet your
`requirements.
`41 3 ROTERP: An interpretive Language for Robot
`Control by Gary Liming l High-level languages may help
`bridge the gap between artificial intelligence and the home
`experimenters robot.
`4-36 Using SOUND Arguments for High-Precision
`RTTY by Scott Persson i How to generate radioteletype
`audio frequencies from an Atari 800.
`453 Binary-Format Number Storage on the Apple II
`Disk by David Eyes i A machine-language routine to read
`and write binary data to a text file.
`
`Reader Service
`
`26 Build the ECM—iOB, an OriginatelAnswer
`Modern by Steve Ciarcial The Texas Instruments
`TMS99532 forms the heart of a Bell—iO3—compatible
`modem.
`
`34 The Enhanced Vic-20, Part 2: Adding a
`3K—Byte Memory Board by Joel Swank l Supplement the
`Vic—20‘s standard 5K bytes of RAM and eliminate those
`annoying ”out-of-memory” messages.
`44 A User’s View of COMDEX by Jerry Pournellel
`An impressionistic report of one of the largest gatherings of
`computer dealers and manufacturers.
`56 The Promise of Perpendicular Magnetic
`Recording by Clark E. Johnson Jr. i As the Japanese
`seem to have realized already. FMR represents the next
`level of recording technology.
`68 New Developments in Floppy Disks by Tom
`Moran i New advances in floppy—diskorive technology
`spurs intense cempetition.
`36 Optical-Memory Media by Edward Rothchildl
`Some background on how optical disks work. who makes
`them. and how much data they can hold.
`II 1 0 Will Removable Hard Disks Replace the
`Floppy? by Larry Sariskyi improved data=storage
`technologies may eventually eliminate floppy disks.
`1 22 The Winchester Odyssey, From Manufacturer
`to User by Jim Toreson i A look at drives. GEMS. and the
`cost of doing business.
`1 30 Building a Hard-Disk interface for an 5-100
`Bus System. Part i: introduction by Andrew C. Cruce
`and Scott A. Alexander i The first in a series of articles on
`
`interfacing a Winchester disk drive to an S—lOO bus CPiM
`microcomputer.
`I 52 NAFLPS: A New Standard for Text and
`Graphics. Part 2: Basic Features by Jim Flemingl How
`to encode text and simple graphics elements in a standard
`and efficient manner.
`
`2 I 8 User's Column: Sage in Bloom. Zeke ll. CBIOS
`Traps. Language Debate Continues by Jerry Pourneliel
`The consummate computer user tackles his new writing
`machine.
`
`262 A Faster Binary Search by Dr. L. E. Larson iAn
`important technique results in faster-running applications
`programs and shorter response times.
`295 Data Collection with a Microcomputer by Dr.
`Mahlon G. Kelly i Using a TBS—BO Model l for environ—
`mental research saves time and money.
`3 10 Build This Memory, Part 1: How to Construct
`a Low-Cost Memory with Ill [6 Memory Devices by
`Cameron Spitzer i Take advantage of the low price of the
`4i it‘s—type memory.
`
`Reviews
`
`190 until H by Stephen Schmitt
`247.. 243, 251 BYTE Game Grid: Project Nebula by
`Keith Carlson: Legionnaire by Gregg Williams; Omega
`Race for the V1020 by Stanley J. Wszola
`256 Ouickcode by Adam B. Green
`232 Hayes's Stack Smartmodem by Norman C. McEntire
`
`Nucleus
`
`6 Editorial: The Software Revolution: Where Will We
`
`Store All Those Programs?
`14 Letters
`
`22 BYTE’s Bugs
`307', 450 Programming Quickies: Add Dimensions to Your
`BASiC: Computing Telescope Parameters with the
`OSI Superboard II
`380, 462 System Notes: Circles and Ellipses on the Apple
`ll: Adding a Trace to North Star BASlC
`4?4 Event Queue
`436 BYTE's Bits
`Software Received
`Ask BYTE
`Books Received
`Clubs and Newsletters
`BYTELlNES
`What's New?
`Unclassified Ads
`BOMB. BOMB Results
`
`
`
`Page 44
`
`Page 152
`
`Page 247
`Page 00002
`
`Page 00002
`
`

`

`Ell
`I‘iii t
`
`Managing Editor
`Mark Haas
`Technical Editors
`
`Gregg Williams. Senior Editor;
`Richard S. Shulortl. Curtis P. Feigel.
`Arthur Little. Stanley Wszola.
`Pamela Clark. Richard Mallory;
`Phillip Lemmons. West Coast Editor; Steve
`Crarcra. Mark Dani-nice. Consulting Editors:
`Jon Swanson. Drafting Editor
`C921 Editors
`Beverly Cronin. Chief.
`Faith Hans‘on. Warren Williamson. Anthony J.
`Lockwood. Hilary Selby Polk. Elizabeth Kepner.
`Nancy Hayes. Cathryn Baskin. Ton-i McMillan.
`Margaret Cooit. Junior Copy Editor
`Assistants
`Faith Kiuntz. Beverly Jackson. Lisa Jo Steiner
`
`Production
`Dawo R. Anderson. Assoc. Director;
`Patrice Scribner. Jan Muller. Virginia Reardon;
`Sherry McCarthy. Chief TypographE'r:
`Debi Fredericks. Donna Sweeney. Valerie Horn
`
`Advertising
`Deborah Porter. Superwsor:
`Marion Carlson. Rob Harlnrngs. Vicki
`Reynolds. Cathy A. R Drew. Lisa Wozniak;
`Patricia Akerley. Reader SENICE Coordinator:
`War Chiu Li. hduertrsrngli’roduction
`Coordinator. Linda J. Sweeney
`Circuits tlon
`
`Gregory Spitzladen. Manager.
`Andrew Jackson, Asst. Manager.
`Agnes E. Perry. Barbara Varnum. Lourse
`Menegus. Jennifer Price. Sheria A. Bamlord.
`James Eingham. Dealer Sales; Deborah J.
`Cadwell, Asst. Linda Ryan
`Marketifl Communications
`Horace T Howtand. Director;
`Wilbur S. Watson. Coordinator.
`Timothy W Taussig. Graphic Pitts Manager;
`Michele P. Venri'lle. Research Manager
`
`Controller's Office
`
`Kenneth A. King. Asst Controller.-
`Maty E. Fluhr. Acct. 8. DP Mgr.- Karen
`Burgess. Jeanne C illey. Linda Fluhr. Vicki
`Bennett. L. Bradley Browne. Vern Rockwell
`Business Manager
`Daniel Rodrigues
`
`Traffic
`N. Scott Gagnon. Manager.-
`Scott Jackson. Kathleen Reckart
`
`Rflgflldfllst
`J86 nann Waters
`Publishers
`Virginia Londoner. Gordon R‘. Williamson.
`John E Hayes. Associate Publisher:
`Cheryl A Hurt]. Publisher's Assistant
`
`
`
`Officers of McGraw-Hill Publications Com-
`pany: Paul F. McPherson. PreSIdent.‘ Executive
`Vice President: Gene W. Simpson; Senior Vice
`President-Editorial: Ralph
`R. Schulz; Vice
`Presidents: Kemp Andersm'l. Business Systems
`Development; Shel F. Asen. Manufaccurin .'
`Harry L. Brown. Special Markets: James
`.
`Hackett, Controller: Eric B. Herr. Planning and
`Development; H. John Sweger. Jr.. Marketing.
`Officers oi
`the Corporation: Harold W.
`McGraw Jr.. Chairman and Chief Executive
`Officer: Joseph L. Dionne. President and Chief
`Operating Officer; Robert N. Landes. Senior Vice
`President
`and Secretary; Ralph
`J. Webb.
`Treasurer.
`
`1!
`
`March 1983 to BYTE Publications Inc
`
`
`
`In Thle lull.
`Sophlm new operating systems and multitasking software promise to
`alter significantly the way we use personal computers. Because of the large
`memory requirements of the new We. we're sure to see changes lor'the
`better in the nature of external storage devices. NM'mogu for mass
`storage will become even more critical as the software revolution continues to
`escalate. As Robert Tlnney‘s cover suggests. personal computers will steed a
`large quantity of high-speed mass storage to hold all the software and outer
`data that we'll generate. Our theme articles address the laeest developments
`in niass storage. Clark E. Johnson Jr. discusses "The Promise of Perpendicular
`Magnetic Recording," Tom Moran looks at "New BMW in Floppy
`Disks.” Edward Rodrchiid writes about "Optical-Memory ltlledla," Larry
`Sarlsky explores the question "Will Restrovable Hard Disks Replace the Flop-
`py?“ Jim Toresori comentrm on “The Winchester Gdysoey." and in the rim
`of a three-part series Andrew C. CW and Scott A. Alexander discuss
`“Elliott-lg a Hard—Disk Interface for an S-I'OO Bus System." Plus we have part 2
`of "NAPLPS. A New Standard for Text and Graphics." the second installment
`in the VIC-20 series. “Adding a 3K-Byse Mommy Board," a review of Wild ll
`from Digital Research and BYTE”: Game Grid. Steve Ciarcla mils you how to
`"Build the ECM-loa. an Originator-Answer Modem," and more.
`
`
`
`
`
`BYTE is published monthly by McGraw-Hill. inc . With offices at T0 Mam St. Peterborough NH 03458. phone
`[603] 924-928I Office hours: Mon-Thur 8:30 AM - 4:30 PM, Frrciay 3.30 AM — Noon. Eastern Time. Address
`subscriptions. change or address. USPS Form 35T9. and fulfillment questions to BYTE Subscriptions. POB 590.
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`Europe. 53? surface delivery elsewhere. Air dElIUEry to selected areas at additional rates upon request. Single copy
`price i5 $2.95 in the USA and its possessions. $3.50 in Canada and Mexico. 54.50 in Europe. and $5.00
`elsewhere Foreign su bscnptrons and sales should be remitted in United States funds drawn on a US bank. Printed
`in United States of America.
`Address all editorial correspondence to the editor at BYTE. PUB 3?2. Hancock NH 03449. Unacceptable
`manuscripts Wlll be returned if accompanied by sufiioenr first class postage. Not responsible for lost manuscripts or
`Dhotos. Opinions expressed by the authors are not necessarily those of BYTE. Entire contents copyright “’9 i933
`by BYTE Publications Inc. Ni rights reserved. Where necessary, permission rs granted by the copyright owner for
`libraries and others reqrsterecl With the Copyright Clearance Center [CCCi to photocopy any article herein for the
`base Fee or 5 i .00 per copy or the article or item plus 25 cents per page. Payment should be sent directly to the
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`the publisher.
`E'irTE‘lo is available in microforrn from University Microfilms international. 300 N Zeeb Rd. Dept PR. Ann
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`Subscription questions or problems should be addressed to:
`BYTE Subscriber Service
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`
`@
`
`Page 00003
`
`Page 00003
`
`

`

`Will Removable Hard Disks
`Replace the Floppy?
`Improved data-storage technologies may eventually
`eliminate floppy disks.
`
`Larry Salinity
`Syquest Technology
`47923 Warm Springs Blvd.
`Fremont, CA 94539
`
`The floppy-disk drive has been the
`method of choice for data storage for
`several years now. But
`like all de
`facto standards, its dominance is be-
`ing challenged,
`in this case by the
`development
`of
`a new storage
`medium—the removable hard-disk
`
`cartridge.
`The cartridge appears to offer all
`the advantages of the floppy disk as
`well as increased storage capacity and
`access speed. But before describing
`this new method of data storage, let's
`take a look at how and why floppy
`disks were developed.
`When IBM introduced the
`
`low-
`their
`System/360 computers,
`level microcode programs were
`
`About the Author
`Larry Sarislry is the utapresident of sales and
`marketing for Syquest Technology. He has
`more than 12 years' experience in marketing
`data-storage products.
`
`110 March 1933 @I ME Publications bu:
`
`stored in read—only memory (ROM).
`By the
`time
`the
`IBM 370 was
`developed, however, semiconductor
`technology had advanced so far that
`microcode
`storage
`could be
`im-
`plemented in semiconductor
`memory. This memory was volatile,
`
`Newer microprocessors
`can make use of
`
`virtual storage only
`with the faster access
`
`speeds offered by hard
`disks.
`
`
`
`so a microcode Ioading—and-storage
`device was necessary. Magnetic tape
`was considered, but
`the need for
`
`loading diagnostic programs as well
`as microcode presented a problem. So
`in 1973. IBM developed a cheap disk
`
`and drive that provided the random-
`access speed needed for diagnostic—
`program loading. This low-cost, flex-
`ible disk gave IBM an economical
`random-access program-loading
`device. And once such a device was
`
`available, it was easy to add a write
`capability for data storage. Sen-licen-
`ductor technology and the IBM 370
`had set the stage for the floppy disk,
`the data-storage medium that helped
`launch the small—computer
`revolu-
`tion.
`
`however, was
`revolution,
`The
`spearheaded not by IBM but by in—
`dependent manufacturers of floppy
`disks such as Shugart Associates and
`Memorex, who saw the value of low-
`cost,
`random—access
`storage for
`smaller computers. By 1975, 27 in-
`dependent suppliers were producing
`8—irlch HOPPY-diSk drives.
`storage
`The new medium for
`offered potent
`advantages. As
`
`Page 00004
`
`Page 00004
`
`

`

`
`
`Photo 1: A size comparison of the 3.9-inch removable hard-disk cartridge drive with
`standard 51/4- and 8-inch floppy-disk drives. The cartridge drive is 1.625 by 4.8 by 3
`inches.
`
`Business Week reported in a May 17,
`1976, article, ”Each standard disk
`(floppy) has the data-storage capacity
`of 3000 punched cards. The disks are
`also reusable, easier
`to store and
`
`mail, and inexpensive." The article
`also predicted that "a new market
`segment is opening up thanks to the
`development of the cheapest of com-
`puters—the microprocessor or com-
`pu ter-on-a-chip. "
`As
`these prophetic words were
`
`written, Shugart Associates was
`developing a
`lower-cost Sid-inch
`flexible-disk drive. It was this drive
`
`that signaled the decline of cassette
`tape. The Sid-inch floppy—disk drives
`and media cost less than comparable
`cassette-based storage. They offered
`an average access time of about half a
`second compared to the cassette’s 20
`seconds. And their error rate was two
`
`orders of magnitude better than that
`of cassettes.
`
`The Winchester Disk
`
`While lower-cost Ski-inch floppy
`disks gained most of the attention in
`1976, Memorex saw another IBM-
`
`developed storage technology that
`could be used in small computers. lts
`Model 601 hard disk was the first
`
`system to be
`small Winchester
`available from a source other than
`
`IBM. By protecting the read/write
`heads and disk platters in a sealed en-
`vironment,
`the Winchester
`could
`deliver higher data-storage capacities.
`faster access, and greater reliability at
`a lower cost per byte. While the 601’s
`disk diameter was a hefty 14 inches,
`successive Winchester—technology
`disk drives reduced it to 3 inches and
`then 5% inches.
`
`The history of disk storage has
`been a tale of increasing compactness.
`The first 14-inch Winchester-type
`drives paralleled established storage-
`module devices. The 8-inch Win-
`
`chester followed the 8-inch floppy
`disk. The Sl/a-inch drive was com-
`
`patible in size with its corresponding
`
`
`
`NEC distributors
`pull miracles out of
`O Thimble.
`
`It’s not Magic, it’s NEC.
`
`
`
`
`NEC information Systems. inc.
`
`Page 00005
`
`Page 00005
`
`

`

`the
`finally,
`floppy disk. And,
`(see
`3.9—inch hard-disk cartridge
`photo 1) parallels
`the newer
`”microfloppies."
`
`The Need for Better Disks
`
`The development of 16-bit pro-
`cessors, more
`complex operating
`systems, and multiuser, multitasking
`configurations has increased the need
`for hard-disk capacity,
`reliability,
`and speed. Newer processors can
`make use of virtual storage only with
`the faster access speeds of hard disks.
`Operating systems
`such
`as Unix
`have a large assortment of utilities
`that won't fit on a floppy. To perform
`multiple tasks for multiple users,
`systems required the capacity and ac-
`cess speed available only from hard
`disks.
`
`if a fixed disk crashes.
`it can be replaced only
`by a factory technician.
`
`
`
`The Limitations of Fixed Disks
`While fixed~disk Winchester drives
`
`are suitable for many applications,
`they present severe integration prob
`lems for smaller computer systems
`that now use one or two Sl/r-inch
`
`Database~management systems, corn—
`puter graphics, English-language-
`based programming, extensive menus,
`and broad-based application packages
`all require faster access to a larger
`amount of data than a single floppy
`disk can hold.
`
`chester drives have proved to be more
`practical for small systems, but they
`are no panacea. Although they’re
`smaller than the 14-inch drives, they
`still may be too large for
`some
`systems. Why? Because most systems
`have required both removable and
`fixed media. If the current system has
`been designed for one or two 51/4 -inch
`floppy disks, there may not be room
`to add a fixed~disk drive.
`
`The user must also worry about the
`possibility of a fixed-disk failure. If
`the fixed disk crashes,
`it can be
`replaced only by a trained technician.
`Even worse, data may be lost forever.
`For this reason, mast users back up
`important programs and files on flop-
`py disks or tape. Unfortunately, the
`floppy disk is often inadequate for
`backup. Small Winchester drives
`are
`applications
`Microcomputer
`floppy—disk drives. The 14-inch drive
`have capacities that range from 5 to
`becoming far more sophisticated. A
`is simply too big and too heavy to be
`80 megabytes. Backing up that much
`business accounting system can re-
`integrated into many existing
`storage on floppy disks is inconve»
`quire a box of 10 floppy disks. A
`systems.
`It also requires
`a more
`nient and slow. And although tape
`high—resolution digitizing camera
`sophisticated interface and both AC
`can be used for backup,
`it lacks the
`may need more than 3 megabyte of
`and DC power—supply voltages.
`random access,
`reliability, and ser-
`The smaller 51/4- and 8—inch Win-
`data storage for a single picture.
`viceability of disk storage.
`
`
` fl-Is'mm lit.
`
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`
` Page 00006
`
`Page 00006
`
`

`

`
`
`Photo 2: 5yquest Technology SQ—Sflo removebie-cartridge hard-disk drive. The car—
`tridge (shown at left) is inserted into the drive unit. shown with its top cover and drive
`door removed.
`
`In spite of these limitations, small
`hard-disk drives have become the
`
`in data storage.
`hottest products
`Almost every computer manufacturer
`now.r
`offers Winchester hard-disk
`
`a
`
`The Hard-Disk Cartridge
`in-
`Floppy disks can no longer
`herently claim thOse advantages over
`hard disks,
`following the develop-
`ment
`of
`new generation of
`removable,
`pocket-sized hard-disk
`storage, as either a standard system
`Although all three sizes are gaining
`cartridges and drives such as the Sy-
`component or an option. Why, then,
`acceptance, many industry analysts
`quest SQ—306. Cartridges can be
`are floppy disks still needed? Because,
`beiieve that only the 3.9-inch hard-
`replaced when they’re full, and,
`like
`until
`recently,
`they enjoyed two
`disk cartridge is inexpensive enough
`floppy disks, they can be transported
`critical advantages over hard disks:
`to compete with floppy-disk drives
`from one computer to another (see
`they were removable and cheap.
`
`
`photo 2}. [Editor’s NotezThe Syquest
`removable-cartridge hard-disk drive
`is not :1 Winchester drive because the
`
`read/write heads are not permanentiy
`sealed with the disk, as is the case in
`
`true Winchester
`R. S. 5.]
`
`technology
`
`But not all hard~disk cartridges can
`compete with the floppy disk. Car-
`tridge drives are now available in
`three sizes: 3.9, 5/4, and 8 inches. All
`three sizes share the same basic tech—
`
`their prices differ sig-
`nology, but
`nificantly. Eight-inch cartridge drives
`crust $1500 or more. The smaller
`Sift—inch drives cost more than $1000.
`The still smaller 3.9-inch drives cost
`
`less than $300. Smaller cartridges also
`cost
`less. The 8—inch cartridge can
`cost more than $100,
`the Sta-inch
`about $50, and the 3.9winch about
`$35.
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`Page 00007
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`Page 00007
`
`

`

`and media. The drive costs only
`slightly more than a
`floppy-disk
`drive. The cost of a cartridge is com-
`parable to the cost of a box of 10 flop-
`py disks.
`This comparison is even more
`favorable in terms of cost per byte
`because the hard-disk cartridge sup-
`plies
`far more capacity per unit.
`While floppy disks can hold up to 1
`megabyte of storage before format-
`ting, the 3.9«inch hard disk has an un-
`formatted capacity of 6.38 mega-
`bytes. Not only does it carry from 6
`to 15 times more data than a floppy
`disk,
`it carries it more safely, sealed
`in a protective cartridge.
`While floppy-disk technology has
`matured and offers few opportunities
`for enhancement, small hard disks are
`at
`the beginning of
`their product-
`technology cycle and will have their
`data storage capacity increased again
`and again. The cost per megabyte of
`storage is dropping rapidly.
`Like audio- and Video-tape cas-
`disk and provides the sector-mark
`settes, hard—disk cartridges will be
`signals and timing information for all
`drives can ocCupy one conventional
`available in a variety of capacities.
`read/ write operations.
`Sid-inch floppy space. The drives are
`
`
`data and provides flexibility in sector
`formatting. This
`enables
`system
`builders to define the number of bytes
`per sector to match any format re—
`quirement.
`The digital servo, helped by orb-
`board microprocessor control and a
`microstepping head positioner, also
`speeds data access and improves ac-
`curacy. The microstepping positioner
`steps in increments of 0.9 degrees
`rather
`than the conventional 1.8
`
`The digital servo system locks the
`read/ write heads over the centerline
`
`of the appropriate recording track.
`More practical
`than conventional
`track-following systems,
`the digital
`servo leaves both surfaces free for
`
`degrees. The drive's microprocessor
`reads servo information, corrects for
`
`track alignment, and adjusts the step-
`per within 100 microinches. all at 60
`times a second.
`
`The 3.9-inch disk drives mount
`
`almost anywhere—under a keyboard
`or
`in a terminal. Two hard-disk
`
`is already
`for example,
`Syqnest,
`developing a cartridge. compatible in
`size with existing cartridges, that will
`double capacity to 12.76 megabytes.
`Regardless of capacity,
`these car-
`tridges deliver better performance
`than floppy disks. Their average ac~
`cess time is 75 milliseconds, or from
`1.5 to 3 times faster
`than floppy
`disks. The data-transfer rate is even
`
`more impressive. In one second, the
`cartridge drive
`can
`transfer
`5
`megabits, compared to the Sly/winch
`disk's 1/: of a megabit. That’s 20 times
`faster.
`
`Cartridge models provide better in-
`terchangeability between drives than
`floppy disks. The cartridge is de-
`signed to provide for a minimum of
`10,000 insertion/removal cycles (see
`figure 1). A closed-loop embedded
`digital servomechanism ensures car-
`tridge interchangeability while allow-
`ing variable sectoring. The embedded
`servo information is recorded on the
`
`
`
`
`
`-
`
`
`
`
`
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`
`Page 00008
`
`Page 00008
`
`

`

`sssemrc, 4pm.
`masserlc mm, Spin
`
`
`
`ELECTROLESS NICKEL,
`805 Iu-In
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`DESK CROSS SECTION
`
`“s.
`
`..
`
`5 \mscarnou CHllNNEL
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`
`DOOR SLIDES T0 LEFT
`FDR HEAD ACCESS
`
`HEEDS RETRnCT
`TO TRACK 000 FOR
`CARTRlDGE FNSERTIDN
`
`TABS
`(nor VISIBLE}
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`REGISTRATlDN DIEMETER
`
`want—PROTECT us
`
`Figure 1: As a cartridge is inserted into the hard-disk drive. the cartridge door slides
`open to allow access to the read/write heads, which were previously retracted to track
`000. The disk is seated onto the drive spindle by a metal scroll on the cartridge (not visi-
`ble in the figure) and then secured by a magnetic hub. Tabs on the drive base ensure that
`the cartridge is inserted correctly and that the cartridge door is open. A cross section of
`the hard disk illustrates the layers of materials on the disk {not drawn to scale}.
`
`Thin-Film Plating
`The 3.9-inch hard-disk cartridge
`can store more data more reliably and
`in less room because it uses thin-film
`
`the magnetic data-
`plating for
`recording layer. While conventional
`Winchester technology must seal the
`disks away from dust, smoke, and
`other contaminants,
`the cartridges
`graphite-coated thin-film metallic
`alloy needs less protection. This thin-
`film plating, with a
`lubricating
`coating that
`shields against dirt,
`allows denser packing of data and
`protects the disk from "head crashes.”
`This plating also eliminates
`the
`need for an initializing purge cycle.
`Users do not have to suffer the in-
`
`long waits before
`convenience of
`beginning operation. (With conven-
`tional hard disks, filtered air is first
`blown over the surface of the disk to
`
`remove any pOSsible contaminants.
`This purge cycle can take several
`minutes.) The thin-film recording
`medium provides greater data densi-
`ty, a more consistent recording sur—
`face, better magnetic resolution, less
`susceptibility to contamination, and
`greater durability than the conven-
`tional ferric—oxide recording medium.
`Let's take a closer look at these ad—
`
`vantages. Thin-film technology in-
`creases data density.
`It
`increases
`storage capacity beyond the current
`limitations of
`the standard Win-
`
`only 1.625 inches high, 4.8 inches
`wide, and 8 inches deep. Their rugged
`design enables them to be used in
`portable systems.
`
`Easy Integration
`The 3.9-inch cartridge has the same
`pinouts,
`timing, data-transfer rates,
`and track/sector
`formatting as
`industry-standard Sl/a—inch fixed-disk
`Winchester drives. This compatibility
`allows the use of standard Winchester
`
`and interfacing pro—
`controllers
`cedures, as well as standard Sid-inch
`floppy—disk DC power supplies.
`
`Convenience
`
`Convenience of use is an important
`factor in the success of the cartridge.
`The 3.9-inch cartridge is a more con-
`venient size than 8-inch floppy disks
`or
`larger cartridges. Just under 4
`inches in length and width and less
`than 1/:
`inch high,
`it fits in a coat
`pocket.
`purse,
`or briefcase.
`Its
`
`116 March 1983 © BYTE Publication-n inc
`
`"unbendable" case is easy to handle
`and safer to mail.
`
`Perhaps more important is the con-
`venience of direct access to more
`data. The user can retrieve data from
`
`chester or floppy disk. While the con-
`ventional medium at 20 to 30 micro-
`inches of thickness has a maximum
`
`a larger online database without in-
`
`The thin-flIm-platlng
`technique used on
`3.9-lnch hard disks
`
`ellmlnates the need for
`
`an Initial purge cycle.
`whlch with
`
`conventlonal disks can
`
`take several minutes.
`
`
`serting and removing many floppy
`disks. This is especially important in
`such applications as accounting,
`in-
`ventory control, database searches,
`and so on.
`
`density of only 8000 flux reversals per
`inch,
`thin film is an order of
`
`magnitude thinner and can store
`more than 20,0CD flux reversals per
`inch. This means simply that thin film
`can increase data density by 2.5
`times. Thin film maintains a more
`
`recording surface. The
`consistent
`conventional medium is limited by its
`uneven thickness and a soft surface
`
`that can be damaged in the event of a
`head crash.
`
`Thin film offers higher resolution
`Expressed as a percentage, the typical
`disk recording medium has a resolu-
`tion of 65 percent. In contrast,
`the
`metal-film medium has a resolution
`
`of 80 perCent. {Resolution is defined
`as the read—back voltage ratio of a
`signal recorded at twice the normal
`
`Page 00009
`
`Page 00009
`
`

`

`recording frequency versus the nor-
`mal recording-frequency signal.)
`Thin film is more durable.
`
`Durability, expressed in terms of sen-
`sitivity to head impact,
`is another
`critical factor. Soft oxide coatings are
`no match for a read/write head.
`
`When a head crashes {contacts the
`
`disks surface}, oxide particles are
`dislodged. These particles can lead to
`still more crashes or surface damage.
`Although it's not as hard as a
`read/write head, metal film is 1000
`times harder than an oxide layer. This
`greater degree
`of hardness
`is
`measured by the Mobs test, which
`scales degrees of hardness from 1 to
`10. Each increasing degree on the
`scale
`represents
`an order
`of
`magnitude increase. A typical
`read/write head has a Mohs number
`of 7. The conventional medium has a
`Mohs number of 2.0 to 2.5. Metal
`film has a hardness of 5.0 to 5.5.
`
`and captured by the fluid lubricant
`used over the ferric-oxide layer. This
`presents operating problems,
`especially for oxide media used in
`Winchester-type disk drives with
`low-flying heads. In such drives, a
`purge cycle of one to two minutes is
`required.
`Some manufacturers of thinnfilm
`
`disks add a layer of graphite, quartz,
`or sapphire above the metal magnetic
`layer. Depending on the loading force
`of the heads used with the disk drive,
`the protective layer can range be-
`tween 0.025 micron and 0.1 micron.
`
`the
`(The heavier the loading force,
`thicker
`the protective
`layer.)
`Microdisk of Fremont, California, a
`
`sister company to Syquest, adds a
`ELI-micron graphite overcoat. The
`dry lubricant affords extra protection
`against head crashes and seals the
`metal substrate to prevent corrosion.
`
`counterparts, but the cost per byte is
`comparable. The
`removable—car-
`tridge user gains online access to
`more data,
`faster
`access
`speed,
`greater dri