Timeline of Binary Prefixes - 1970s

1970s

1970
  • "The following are excerpts from an IBM Data Processing Division press technical fact sheet distributed on June 30, 1970.
    • Users of the Model 165 will have a choice of five main core storage sizes, ranging from 512,000 to over 3-million bytes. Seven main memory sizes are available for the Model 155, ranging from 256,000 to over 2-million bytes."
  • Weiler, Paul W.; Richard S. Kopp, Richard G. Dorman (May 1970). "A Real-Time Operating System for Manned Spaceflight". Computers, IEEE Transactions on 19 (5): 388–398. doi:10.1109/T-C.1970.222936. ISSN 0018-9340. "Each of the five system/360 model 75 computers (Fig. 2) has one megabyte of primary core storage plus four megabytes of large core storage (LCS, IBM 2361)."
1971
  • IBM System/360 Operating System: Storage Estimates uses K in a binary sense approximately 450 times, such as ""System/360 Configuration: Model 40 with 64K bytes of storage and storage protection." Note the letter "K" is also sometimes used as a variable in this document (see page 23).
1972
September
  • Lin and Mattson introduce the term Mbyte.
    • Lin, Yeong; Mattson, Richard (September 1972). "Cost-performance evaluation of memory hierarchies". Magnetics, IEEE Transactions on (IEEE) 8 (3): pg 390–392. Bibcode:1972ITM.....8..390L. doi:10.1109/TMAG.1972.1067329. "Also, random access devices are advantageous over serial access devices for backing store applications only when the memory capacity is less than 1 Mbyte. For capacities of 4 Mbyte and 16 Mbyte serial access stores with shift register lengths of 256 bit and 1024 bit, respectively, look favorable."
1973
  • Habib, Stanley (October 1973). "Notes from industry". ACM SIGMICRO Newsletter (ACM Press) 4 (3): pg 29. doi:10.1145/1217132.1217137. .
    • OCEANPORT, N.J., SEPT. 25, 1973 – A 16-bit minicomputer priced at under $2,000.00 in quantities and a 32-bit minicomputer priced at under $6,000.00 in quantities were introduced today by Interdata, Inc. The 16-bit mini, the Model 7/16, includes an 8KB memory unit in its basic configuration, and will be available for delivery in the first quarter of 1974. The single unit price of the 7/16 is $3,200.00. The 32-bit mini, the Model 7/32, includes a 32KB memory unit and will be available for delivery in the second quarter of 1974. The single unit price of the 7/32 is $9,950.00.
  • DEC PDP-11/40 Manual
    • "Direct addressing of 32K 16-bit words or 64K 8-bit bytes (K = 1024)" (Page 1-1) Contrast the 1969 PDP-11 Handbook, which avoids this usage almost everywhere. (Above)
1974
  • The seminal 1974 Winchester HDD article which makes extensive use of Mbytes with M being used in the conventional, 106 sense. Arguably all of today's HDD's derive from this technology.
  • The October 1974 CDC Product Line Card unambiguously uses MB to characterize HDD capacity in millions of bytes.
1975
  • The 15th CGPM defines the SI prefixes peta, and exa as 1015 and 1018.
  • Byte Magazine December 1975 article on IBM 5100 includes the following:
    • "User memory starts at 16K bytes in the minimum configuration and can be expanded to 64K bytes (65,536)."
  • Gordon Bell uses the term megabytes:
    • Bell, Gordon; Strecker, William (November 1975). "Computer structures: What have we learned from the PDP-11?" (PDF). ISCA '76: Proceedings of the 3rd annual symposium on Computer architecture (ACM Press): pg 1–14. doi:10.1145/800110.803541. "memory size (8k bytes to 4 megabytes)."
1976
  • DEC RK05/RK05J/RK05F disk drive maintenance manual
    • "Bit Capacities (unformatted)" "25 million" | "50 million" (57,600 bits/ track * 406 | 812 tracks = 23,385,600 | 46,771,200 bits)
  • The Memorex 1976 annual report has 10 instances of the use of megabyte to describe storage devices and media.
  • Caleus Model 206-306 Maintenance Manual uses 3MB to characterize a drive having 3,060,000 bytes capacity.
  • The first 5¼ inch floppy disk drive, the Shugart SA 400, is introduced in August 1976. The drive had 35 tracks and was single sided. The data sheet gives the unformatted capacity as 3125 bytes per track for a total of 109.4 Kbytes (3125 × 35 = 109,375). When formatted with 256 byte sectors and 10 sectors per track the capacity is 89.6 Kbytes (256 × 10 × 35 = 89,600).
1977
  • HP 7905A Disc Drive Operator's Manual
    • "nearly 15 million bytes" with no other abbreviations
  • 1977 Disk/Trend Report – Rigid Disk Drives, published June 1977
    • This first edition of the annual report on the hard disk drive industry makes extensive use of MB as 106 bytes. The industry, in 1977, is segmented into nine segments ranging from "Disk Cartridge Drives, up to 12 MB" to "Fixed Disk Drives, over 200 MB." While the categories changed during the next 22 years of publication, Disk/Trend, the principal marketing study of the hard disk drive industry always and consistently categorized the industry in segments using prefixes M and later G in the decimal sense.
  • VAX11/780 Architecture Handbook 1977–78. Copyright 1977 Digital Equipment Corporation.
    • Page 2-1 "physical address space of 1 gigabyte (30 bits of address)" The initial hardware was limited to 2 M bytes of memory utilizing the 4K MOS RAM chips. The VAX11/780 handbooks use M byte and Mbyte in the same paragraph.
1978
  • DEC RM02/03 Adapter Technical Description Manual
    • "The RM02 or RM03 Disk Drive (Figure 1-1) is an 80M byte (unformatted; 67M byte formatted) … storage device … in the 16-bit format, the maximum storage capacity is 33,710,080 data words per disk pack" (33,710,080 * 16/8 = 67,420,160 8-bit bytes)
1979
  • Fujitsu M228X Manual
    • "Storage capacity (unformatted)" "67.4 MB", "84.2 MB", etc.
    • "20,480 Bytes" per track, 4 tracks per cylinder, 808+15 cylinders = 67,420,160 bytes
  • Sperry Univac Series V77 Microcomputer Systems Brochure, Circa 1978, Printed July 1979
    • Page 5: Table list memory options as 64KB, 128KB, and 256KB. Memory Expansion is up to 2048KB
    • Page 9: "Memory for the V77-800 is available in 128K byte and 256K byte increments up to a maximum of 2 megabytes "
    • Page 21: Moving Head Disks – units up to 232 million byte disk pack systems. Diskette – storage of 0.5 MB per drive.
  • The following statistics were taken from the December 1979 editions of Byte Magazine and Datamation. The first number is the number of articles or advertisements that used any variant of megabyte for HDDs or Main memory while the second number is the total number of times it was used in the advertisement or article.
Variant Used In Decimal Sense Used In Binary Sense
million 1 / 1
megabyte 9 / 12 1 / 1
MByte or M Byte 3 /10
MB 5 / 18
Mb 2 / 2 1 / 3
M 1 / 1
Total 20 / 43 2 / 4

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