History of hard disk drives

In 1953, IBM recognized the immediate application for what it termed a "Random Access File" having high capacity and rapid random access at a relatively low cost.[1] After considering technologies such as wire matrices, rod arrays, drums, drum arrays, etc.,[1] the engineers at IBM's San Jose California laboratory invented the hard disk drive.[2] The disk drive created a new level in the computer data hierarchy, then termed Random Access Storage but today known as secondary storage, less expensive and slower than main memory (then typically drums) but faster and more expensive than tape drives.[3]

The commercial usage of hard disk drives began in 1957, with the shipment of a production IBM 305 RAMAC system including IBM Model 350 disk storage.[4] US Patent 3,503,060 issued March 24, 1970, and arising from the IBM RAMAC program is generally considered to be the fundamental patent for disk drives.[5]

Each generation of disk drives replaced larger, more sensitive and more cumbersome devices. The earliest drives were usable only in the protected environment of a data center. Later generations progressively reached factories, offices and homes, eventually reaching ubiquity.

Disk media diameter was initially 24-inches in diameter but over time it has been reduced to today's 3.5" and 2.5" standard sizes. Drives with the larger 24-inch and 14-inch diameter media were typically mounted in standalone boxes (resembling washing machines) or large equipment rack enclosures. Individual drives often required high-current AC power due to the large motors required to spin the large disks. Drives with smaller media generally conformed to de facto standard form factors.

The capacity of hard drives has grown exponentially over time. When hard drives became available for personal computers, they offered 5-megabyte capacity. During the mid-1990s the typical hard disk drive for a PC had a capacity of about 1 gigabyte.[6] As of December 2017, desktop hard disk drives typically had a capacity of 1 to 6 terabytes, with the largest-capacity drives reaching 12 terabytes.

Unit production peaked in 2010 at about 650 million units and has been in a slow decline since then

1950s–1970s

The IBM 350 Disk File was developed under the code-name RAMAC by an IBM San Jose team led by Reynold Johnson. It was announced in 1956 with the then new IBM 305 RAMAC computer.[7] A variant, the IBM 355 Disk File, was simultaneously announced with the IBM RAM 650 computer,[8] an enhancement to the IBM 650.

The IBM 350 drive had fifty 24-inch (0.6 m) platters, with a total capacity of five million 6-bit characters (3.75 megabytes).[9] A single head assembly having two heads was used for access to all the platters, yielding an average access time of just under 1 second.

The RAMAC disk drive created a new level in the computer data hierarchy, today known as secondary storage, less expensive and slower than main memory (then typically core or drum) but faster and more expensive than tape drives.[3] Subsequently there was a period of about 20 years in which other technologies competed with disks in the secondary storage marketplace, for example tape strips, e.g., NCR CRAM, tape cartridges, e.g., IBM 3850, and drums, e.g., Burroughs B430, UNIVAC FASTRAND, but all ultimately were displaced by HDDs. Today SSDs compete with HDDs in the marketplace.

The IBM 1301 Disk Storage Unit,[10] announced in 1961, introduced the usage of heads having self-acting air bearings (self-flying heads) with one head per each surface of the disks.

Also in 1961, Bryant Computer Products introduced its 4000 series disk drives. These massive units stood 52 inches (1.3 m) tall, 70 inches (1.8 m) wide, and had up to 26 platters, each 39 inches (0.99 m) in diameter, rotating at up to 1,200 rpm. Access times were from 50 to 205 milliseconds (ms). The drive's total capacity, depending on the number of platters installed, was up to 205,377,600 bytes (205 MB).[11][12]

The first disk drive to use removable media was the IBM 1311 drive. It was introduced in 1962 using the IBM 1316 disk pack to store two million characters. It was followed by the IBM 2311 (1964) using the IBM 1316 disk pack to store 5 megabyte, IBM 2314 (1965) using the IBM 2316 disk pack to store 29 megabytes, the IBM 3330 using 3336 disk packs to store 100 megabytes and the 3330-11 using the 3336-11 to store 200 megabytes.

A partially disassembled IBM 350 (RAMAC)

Memorex in 1968 shipped the first HDD, the Memorex 630, plug compatible to an IBM model 2311 marking the beginning of independent competition (Plug Compatible Manufacturers or PCMs) for HDDs attached to IBM systems. It was followed in 1969 by the Memorex 660, an IBM 2314 compatible, which was OEM'ed to DEC and resold as the RP02.

Removable disk packs

In 1973, IBM introduced the IBM 3340 "Winchester" disk drive and the 3348 data module, the first significant commercial use of low mass and low load heads with lubricated platters and the last IBM disk drive with removable media. This technology and its derivatives remained the standard through 2011. Project head Kenneth Haughton named it after the Winchester 30-30 rifle because it was planned to have two 30 MB spindles; however, the actual product shipped with two spindles for data modules of either 35 MB or 70 MB.[13] The name 'Winchester' and some derivatives are still common in some non-English speaking countries to generally refer to any hard disks (e.g. Hungary, Russia).

Also in 1973, Control Data Corporation introduced the first of its series of SMD disk drives using conventional disk pack technology. The SMD family became the predominant disk drive in the minicomputer market into the 1980s.

Smaller diameter media came into usage during the 1970s and by the end of the decade standard form factors had been established for drives using nominally 8-inch media (e.g., Shugart SA1000) and nominally 5.25-inch media (e.g., Seagate ST-506).

During the 1970s, captive production, dominated by IBM's production for its own use, remained the largest revenue channel for HDDs, though the relative importance of the OEM channel grew. Led by Control Data, Diablo Systems, CalComp and Memorex, the OEM segment reached $631 million in 1979, but still well below the $2.8 billion associated with captive production.[14]

1980s, the transition to the PC era

The 1980s saw the minicomputer age plateau as PCs were introduced. Manufacturers such as DEC and Hewlett-Packard continued to manufacture minicomputer compatible hard drive systems as industry demanded higher storage. Hewlett-Packard introduced the HP 7935 as one such drive. But it was clear that smaller Winchester storage systems were eclipsing large platter hard drives.

Seagate 20 MB HDD and Western Digital Controller for PC

Hard disk drives for personal computers (PCs) were initially a rare and very expensive optional feature; systems typically had only the less expensive floppy disk drives or even cassette tape drives as both secondary storage and transport media. However by the late '80s, hard disk drives were standard on all but the cheapest PC and floppy disks were used almost solely as transport media.

Most hard disk drives in the early 1980s were sold to PC end users by systems integrators such as the Corvus Disk System or the systems manufacturer such as the Apple ProFile. The IBM PC XT in 1983, included an internal standard 10MB hard disk drive, and soon thereafter internal hard disk drives proliferated on personal computers.

HDDs continued to get smaller with the introduction of the 3.5-inch form factor in the middle of the decade Rodime 1983 and the 2.5-inch form factor PrairieTek 1988.

Industry participation peaked with about 75 active manufacturers in 1985 and then declined thereafter even though volume continued to climb: by 1989 reaching 22 million units and $23 billion in revenue.[15]

1990s

Even though there were a number of new entrants, industry participants continued to decline in total to 15 in 1999. Unit volume and industry revenue monotonically increased during the 1990s to 174 million units and $26 billion.[16]

The industry production consolidated around the 3.5-inch and 2.5 inch form factors; the larger form factors dying off while several smaller form factors were offered but achieved limited success, e.g. HP 1.3-inch Kittyhawk, IBM 1-inch Microdrive, etc..

2000 to present

In 2001 the HDD industry experienced its first ever decline in units and revenue.

The number of industry participants decreased to 6 in 2009 and 3 in 2013.

Unit production peaked in 2010 at about 650 million units and has been in a slow decline since then.[17] Shipments in 2017 estimated at about 404 million units.[18]

Timeline

  • 1956 – IBM 350, shipment of test disk drive to Zellerbach, SF CA, USA
  • 1957 – IBM 350, first production disk drive, 5 million characters (6-bit), equivalent to 3.75 megabytes.
  • 1961 – IBM 1301 Disk Storage Unit introduced with one head per surface and aerodynamic flying heads, 28 million characters (6-bit) per module.
  • 1961 – Bryant Computer Products division of Ex-Cell-O, 1 meter platters, 1200 RPM, up to 205MB.
  • 1962 – IBM 1311 introduced removable disk packs containing 6 disks, storing 2 million characters per pack
  • 1964 – IBM 2311 with 7.25 megabytes per disk pack
  • 1964 – IBM 2310 removable cartridge disk drive with 1.02 MB on one disk
  • 1965 – IBM 2314 with 11 disks and 29 MB per disk pack
  • 1968 – Memorex is first to ship an IBM-plug-compatible disk drive
  • 1970 – IBM 3330 Merlin, introduced error correction, 100 MB per disk pack
  • 1973 – IBM 3340 Winchester introduced removable sealed disk packs that included head and arm assembly, 35 or 70 MB per pack
  • 1973 – CDC SMD announced and shipped, 40 MB disk pack
  • 1976 – 1976 IBM 3350 "Madrid" – 317.5 megabytes, eight 14" disks, re-introduction of disk drive with fixed disk media
  • 1979 – IBM 3370 introduced thin film heads, 571 MB, non-removable
  • 1979 – 1979 IBM 62PC "Piccolo" – 64.5 megabytes, six 8" disks, first 8-inch HDD
  • 1980 – The IBM 3380 was the world's first gigabyte-capacity disk drive. Two 1.26 GB, head disk assemblies (essentially two HDDs) were packaged in a cabinet the size of a refrigerator,[19] weighed 455 kg (1000 lb), and had a price tag of 81,000 USD (Model B4) which is 240,579 USD in present-day terms.[20]
  • 1980 – ST-506 first 5​1⁄4 inch drive released with capacity of 5 megabytes, cost $1500 USD
  • 1982 – HP 7935 404 megabyte, 7 platter hard drive for minicomputers, HP-IB bus, $27,000
  • 1983 – RO351/RO352 first 3​1⁄2 inch drive released with capacity of 10 megabytes[21]
  • 1986 – Standardization of SCSI
  • 1988 – PrairieTek 220 – 20 megabytes, two 2.5" disks, first 2.5 inch HDD
  • 1989 – Jimmy Zhu and H. Neal Bertram from UCSD proposed exchange decoupled granular microstructure for thin film disk storage media, still used today.
  • 1990 – 1990 IBM 0681 "Redwing" – 857 megabytes, twelve 5.25" disks. First HDD with PRML Technology (Digital Read Channel with 'partial response maximum likelihood' algorithm).
  • 1991 – IBM 0663 "Corsair" – 1,004 megabytes, eight 3.5" disks; first HDD using magnetoresistive heads
  • 1991 – Integral Peripherals 1820 "Mustang" – 21.4 megabytes, one 1.8" disk, first 1.8-inch HDD[22]
  • 1992 – HP Kittyhawk – 20MB, first 1.3-inch hard-disk drive
  • 1993 – IBM 3390 model 9, the last Single Large Expensive Disk drive announced by IBM
  • 1994 – IBM introduces Laser Textured Landing Zones (LZT)
  • 1997 – IBM Deskstar 16GP "Titan" – 16,800 megabytes, five 3.5" disks; first (Giant Magnetoresistance) heads
  • 1997 – Seagate introduces the first hard drive with fluid bearings[23]
  • 1998 – UltraDMA/33 and ATAPI standardized
  • 1999 – IBM releases the Microdrive in 170 MB and 340 MB capacities
  • 2002 – (Parallel) ATA breaks 137 GB (128 GiB) addressing space barrier
  • 2003 – Serial ATA introduced
  • 2003 – IBM sells disk drive division to Hitachi
  • 2004 – MK2001MTN first 0.85-inch drive released by Toshiba with capacity of 2 gigabytes[22]
  • 2005 – First 500 GB hard drive shipping (Hitachi GST)
  • 2005 – Serial ATA 3 Gbit/s standardized
  • 2005 – Seagate introduces Tunnel MagnetoResistive Read Sensor (TMR) and Thermal Spacing Control
  • 2005 – Introduction of faster SAS (Serial Attached SCSI)
  • 2005 – First perpendicular magnetic recording (PMR) HDD shipped: Toshiba 1.8-inch 40/80 GB[24]
  • 2006 – First 750 GB hard drive (Seagate)
  • 2006 – First 200 GB 2.5" hard drive utilizing perpendicular recording (Toshiba)
  • 2006 – Fujitsu develops heat-assisted magnetic recording (HAMR) that could one day achieve one terabit per square inch densities[25]
  • 2007 – First 1 terabyte[26] hard drive[27] (Hitachi GST)
  • 2008 – First 1.5 terabyte[26] hard drive[28] (Seagate)
  • 2009 – First 2.0 terabyte hard drive[29] (Western Digital)
  • 2010 – First 3.0 terabyte hard drive[30][31] (Seagate, Western Digital)
  • 2010 – First hard drive manufactured by using the Advanced Format of 4,096 bytes a block ("4K") instead of 512 bytes a block[32]
  • 2011 – First 4.0 terabyte hard drive[33] (Seagate)
  • 2011 – Floods hit many hard drive factories. Predictions of a worldwide shortage of hard disk drives cause prices to double.[34][35][36]
  • 2012 – Western Digital announces the first 2.5-inch, 5 mm thick drive, and the first 2.5-inch, 7 mm thick drive with two platters[37] (Western Digital)
  • 2012 – HGST announces helium-filled hard disk drives, promising cooler operation and the ability to increase the maximum number of platters from five to seven in the 3.5" form factor[38] (Hitachi GST)
  • 2012 – TDK demonstrates 2 TB on a single 3.5-inch platter[39]
  • 2012 – Hitachi Global Storage Technologies and Western Digital merge to one hard drive manufacturer. To ensure actual competition on the hard drive market after the merging, the U.S. Federal Trade Commission requires that Western Digital and Hitachi GST give assets and intellectual property rights to Toshiba.[40] This allows Toshiba to re-enter the 3.5" desktop hard disk drive market with capacities up to 3 TB.[41] Prior to this, Toshiba had only manufactured 2.5" laptop HDDs for many years.
  • 2013 – Seagate announces that it will ship hard disk drives with capacities up to 5 TB using shingled magnetic recording (SMR), a method where tracks are written to partially overlap each other. The read head, being smaller, can still read the overlapped tracks.[42]
  • 2013 – HGST announces a helium-filled 6 TB hard disk drive for enterprise applications[43]
  • 2013 – Western Digital demonstrates heat assisted magnetic recording (HAMR) technology[44][45][46][47]
  • 2014 – Seagate introduces 6 TB hard drives that do not use helium, in turn increasing their power consumption and lowering their overall cost[48]
  • 2014 – Seagate ships world's first 8 TB hard drives[49]
  • 2015 – In June HGST ships Ultrastar Archive Ha10 SMR HDD, the world's first 10 TB HDD[50] followed in December by a conventional PMR HDD[51]
  • 2017 – 12 TB Helium-based HDD available from Western Digital.[52]
  • 2017 – 14 TB Helium-filled PMR HDD announced by Toshiba, with availability being promised for 2018 Q1 or Q2.[53]

Manufacturing history

Diagram of consolidation

Manufacturing began in California's Silicon Valley in 1957 with IBM's production shipment of the first HDD, the IBM RAMAC 350. The industry grew slowly at first with three additional companies in the market by 1964, Anelex Corp., Bryant Computer Products and Data Products Corp..[54] The industry grew rapidly in the late 1960s and again in the 1980s reaching a peak of 75 manufacturers in 1984.[55] There have been at least 221 companies manufacturing hard disk drives[56][57][58][59] but most of that industry has vanished through bankruptcy or mergers and acquisitions. Surviving manufacturers are Seagate, Toshiba and Western Digital (WD) with Toshiba as the senior participant having entered the market in 1977,[60] twenty years after IBM started the market.

From beginning and into the early 1980s manufacturing was mainly by US firms in the United States at locations such as Silicon Valley, Los Angeles, Minnesota and Oklahoma City.[57]:Table 7 In the 1980s US firms, beginning with Seagate, began to shift production to Singapore and then other locations in southeast Asia. In a span of seven years, 1983 to 1990, Singapore became the single largest location of HDD production, amounting to 55% of worldwide production.[57]:Table 9 Japanese HDD companies later also moved their production to southeast Asia.[57]:Table 10 Today the three remaining firms all produce their units in the Pacific Rim.

By the 1990s the dollar value of magnetic recording devices produced by companies located in California's "Silicon Valley" exceeded the dollar value of semiconductor devices produced there leading some to suggest that a more appropriate name for this area would be "Iron Oxide Valley," after the magnetic material coating the disks.[61] All three remaining firms still have significant activities in Silicon Valley, but no HDD manufacturing. Western Digital still manufactures its read-write head wafers in Fremont CA.

See also

References

  1. 1 2 "Proposal – Random Access File," A. J. Critchlow, IBM RESEARCH AND DEVELOPMENT LABORATORY, San Jose, California, February 6, 1953
  2. ↑ US 3503060 DIRECT ACCESS MAGNETIC DISC STORAGE DEVICE March 24, 1970, invented by Goddard & Lynott, assigned to IBM
  3. 1 2 The IBM 350 RAMAC Disk File, ASME Award, Feb 27, 1984.
  4. ↑ [Bashe et. al. (1986). IBM's Early Computers. MIT Press. p. 300. ISBN 0-262-02225-7. ]
  5. ↑ Disk Drive Patent Archived 2011-08-28 at the Wayback Machine.
  6. ↑ 1996 Disk Trend Report – Rigid Disk Drives, Figure 2 – Unit Shipment Summary
  7. ↑ "NEW PRODUCT ANNOUNCEMENT- IBM 305 RAMAC," IBM Announcement Letter 256-114, September 4, 1956
  8. ↑ "NEW PRODUCT ANNOUNCEMENT- RAM 650," IBM Announcement Letter 256-117, September 4, 1956
  9. ↑ Jacob, Bruce; Ng, Spencer W.; Wang, David T. (2008). Memory systems: cache, DRAM, disk. Elsevier Inc. p. 602. ISBN 978-0-12-379751-3.
  10. ↑ "IBM Archives: IBM 1301 disk storage unit". www-03.ibm.com. 23 January 2003.
  11. ↑ "Bryant Model 2 Series 4000 Disc Files" (PDF). Bryant Computer Products. 1965-06-15. Retrieved 2010-01-03.
  12. ↑ "Data Storage, Data Backup and Storage Virtualization: Walking Through 50 Years of Hard Disk Drive History (slide 6)". eWEEK.com. Retrieved 2010-01-03.
  13. ↑ "IBM Archives: IBM 3340 direct access storage facility". www.ibm.com. 23 January 2003.
  14. ↑ Storage Industry Dynamics And Strategy Archived 2014-02-09 at the Wayback Machine.
  15. ↑ Disk/Trend Report - Rigid Disk Drives, October 1989
  16. ↑ Gartner/Dataquest, Market Share and Forecast: Hard Disk Drives, Worldwide, 2001-2010, Chapter 2, (c) 2006
  17. ↑ "469 million HDDs Shipped in 2015, 651 million HDDs in 2010 – AnandTech". Storage Newsletter. March 11, 2016. Retrieved March 11, 2016.
  18. ↑ "HDD Shipments Fell to 404 Million in 2017 – Trendfocus". Storagee Newsletter. February 23, 2018. Retrieved August 23, 2018.
  19. ↑ "IBM Arrchives: IBM 3380 direct access storage device". IBM. Retrieved 2015-06-22.
  20. ↑ Federal Reserve Bank of Minneapolis Community Development Project. "Consumer Price Index (estimate) 1800–". Federal Reserve Bank of Minneapolis. Retrieved January 2, 2018.
  21. ↑ http://chmhdd.wetpaint.com/page/Rodime+RO352
  22. 1 2 Rex Farrance (September 13, 2006). "Timeline: 50 Years of Hard Drives". PCWorld.
  23. ↑ http://www.seagate.com/ww/v/index.jsp?locale=en-US&name=Seagate_Forms_Strategic_Partnerships_to_Manufacture_Fluid_Dynamic_Bearing_Motors_for_Hard_Disc_Drives&vgnextoid=be0c0b64f9e3e010VgnVCM100000dd04090aRCRD
  24. ↑ "Toshiba : Press Releases 14 December, 2004". www.toshiba.co.jp.
  25. ↑ http://www.tgdaily.com/content/view/30024/135/
  26. 1 2 "Convert terabytes (TB) to tebibytes (TiB) - Category : bits and bytes - Unit Conversion Center". www.conversioncenter.net.
  27. ↑ "Hitachi Introduces 1-Terabyte Hard Drive". PCWorld.
  28. ↑ "Seagate Powers Next Generation Of Computing With Three New Hard Drives, Including World's First 1.5-Terabyte Desktop PC And Half-Terabyte Notebook PC Hard Drives - News - Seagate US".
  29. ↑ "WD launches industry's first 2 TB hard drives".
  30. ↑ Shimpi, Anand Lal. "The World's First 3TB HDD: Seagate GoFlex Desk 3TB Review".
  31. ↑ "Western Digital, the first to ship an internal 3TB hard drive".
  32. ↑ Ward, Mark (2010-03-09). "Hard drive evolution could hit XP". BBC News.
  33. ↑ Shimpi, Anand Lal. "Seagate Ships World's First 4TB External HDD".
  34. ↑ Fuller, Thomas (6 November 2011). "Thailand Flooding Cripples Hard-Drive Suppliers". New York Times. Retrieved 12 November 2011.
  35. ↑ "Western Digital's flood-hit Thailand ops to hurt company". Reuters. 17 October 2011. Retrieved 29 October 2011.
  36. ↑ "Farming hard drives: how Backblaze weathered the Thailand drive crisis". 2012-10-09.
  37. ↑ "IDF: Western Digital demonstrates 5mm thick hard disks".
  38. ↑ "HGST Announces Radically New, Helium-Filled Hard Disk Drive Platform - HGST". www.hgst.com.
  39. ↑ "TDK Finally Crams 2TB on One 3.5-inch HDD Platter". 4 October 2012.
  40. ↑ "FTC: Western Digital and Hitachi must give assets and IP rights to Toshiba (update: sale approved)".
  41. ↑ "Toshiba Expands Product Portfolio with 3.5-Inch Client Hard Disk Drives ..." (PDF).
  42. ↑ Shimpi, Anand Lal. "Seagate to Ship 5TB HDD in 2014 using Shingled Magnetic Recording".
  43. ↑ DailyTech – HGST Unveils Helium-Filled Enterprise HDDs
  44. ↑ "Seagate hits 1 terabit per square inch, 60TB hard drives on their way - ExtremeTech". 20 March 2012.
  45. ↑ "WD Demos Future HDD Storage Tech: 60TB Hard Drives". Tom's Hardware.
  46. ↑ "Western Digital hoping for 5x larger hard drives with HAMR".
  47. ↑ "This time next year you could be pre-ordering a 60TB HAMR hard drive - Pocket-lint". 15 November 2013.
  48. ↑ "- Seagate Enterprise Capacity 3.5 HDD Datasheet" (PDF).
  49. ↑ "Seagate Ships World's First 8TB Hard Drives - News - Seagate US".
  50. ↑ "HGST Delivers World's First 10TB Enterprise HDD for Active Archive Applications - HGST". www.hgst.com.
  51. ↑ "Western Digital Corporation Is Now Shipping World's First Helium-filled 10TB PMR HDD To Meet Exponential Growth In Data - HGST". www.hgst.com.
  52. ↑ Shilov, Anton. "Western Digital Starts Shipments of HGST Ultrastar He12 12 TB HDDs".
  53. ↑ Shilov, Anton. "Toshiba Announces 14 TB PMR MG07ACA HDD: 9 Platters, Helium-Filled, 260 MB/s".
  54. ↑ Hess, Herman (1964). "A Comparison of the Characteristics of Modern Discs and Tapes". Disc File Applications. Nation's First Disc File Symposium. Detroit, MI, USA: American Data Processing Inc. pp. 60–70. 64-23108.
  55. ↑ Porter, James (October 1984). 1984 Disk/Trend Report - Rigid Disk Drives. Disk/Trend Inc. p. SUM-4.
  56. ↑ Maleval, Jean-Jacques (2013-03-28). "HISTORY: List of 221 Companies in HDD Manufacturing Since 1956". Retrieved 2017-03-27.
  57. 1 2 3 4 McKendrick, David (November 1997). "Sustaining Competitive Advantage in Global Industries: Technological Change and Foreign Assembly in the Hard Disk Drive Industry". Archived from the original on 2014-02-09. Retrieved 2011-08-03. McKendrick lists 67 defunct hard disk drive manufacturers
  58. ↑ "TheRef - Hard Drives". TheRef lists 101 HDD manufacturers active from 1989 to 1996, only three of which remain in 2017.
  59. ↑ "硬盘" [Hard disk manufacturers] (in Chinese and English). Archived from the original on 2016-12-06. Retrieved 2017-03-30. - lists 126 HDD manufacturers including 3 current ones.
  60. ↑ "Toshiba MK-100F/MK-300F". IPSJ Computer Museum. Retrieved April 18, 2017. This was a 14-inch fixed magnetic disk unit Toshiba started shipping in June 1977
  61. ↑ Livingston, James D. (1996). DRIVING FORCE - The Natural Magic Of Magnets. Harvard University Press. p. 148.
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