IBM Portable PC
Introduced:September, 1975
Price: US $19,975 w/ 64K RAM
Weight:55 pounds
CPU:IBM proprietary, 1.9MHz
RAM:16K, 64K max
Display:5" monochrome monitor
64 X 16 text
Storage:Internal 200K tape (DC300)
Ports:tape / printer I/O port
Serial #:
BASIC:  10-11503
APL: 10-13616

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The Model 5100 is IBM's first minicomputer, i.e. not a mainframe, and is also considered one of the world's first portable computers. It is preceded only by the Hewlett-Packard HP-9830A from 1973. Although at 55-pounds, the 5100 might best be described as "self-contained" rather than "portable".

There were very few other computers available at the time, and nothing even close to the capabilities of the 5100. It is a very complete system - with a keyboard, built-in data storage, and a full-screen display. It was also very expensive - up to US$20,000. It was specifically designed for professional and scientific problem-solvers, not business users or hobbyists.

There are twelve different models of the 5100.
They were all rather expensive:
MemoryProgramming language
16KA1 - $8,975B1 - $9,975C1 - $10,975
32KA2 - $11,975B2 - $12,975C2 - $13,975
48KA3 - $14,975B3 - $15,975C3 - $16,975
64KA4 - $17,975B4 - $18,975C4 - $19,975

Depending on options installed, the 5100 can run the APL and/or BASIC programming languages.
What is APL? It is a programming language which used to be run only on mainframe computers (what else was there?)
Here are some links describing it:

  • Apparently, APL was a difficult task for IBM to accomplish with an interpreter in the 5100, so instead they wrote an emulation program so that the S/360 mainframe version of APL could be run instead -- The 5100 is like a desktop IBM S/360 mainframe computer which only runs APL.

    Opening the 5100, you encounter an upside-down circuit board with thousands of sharp wires sticking straight up.

    What are they? This is the bottom of the backplane in which all of the circuit board plug into.

    Some jumpers can also be installed here for different configuration options.

    As seen below, it swings open on hinges to allow access the circuit boards, and for easy access to all of the other system components.

    In 1978, IBM 5100 was superseded by the IBM 5110 line of computers.

    Most of the circuit boards have unusual IBM proprietary silver-colored metal integrated circuit (IC) chips.

    There isn't a discrete CPU (Central Processing Unit) as in modern computers, the circuit board seen below is the "processor" - it has over 15 large chips.

    Caption: "HAYSTACK IN THE NEEDLE - This computer chip contains 48,000 separate bits of information, yet it fits inside the eye of a common sewing needle.

    Such chips made possible IBM's new, 50-pound portable computer which can be carried to the business problems it was designed to solve."

    Related Links

  • IBM 5100 manuals!
  • IBM 5100 from
  • IBM 5100 - lots of pics!
  • IBM 5100 from Eric's Retrocomputing
  • IBM 5100 from The Obsolete Computer Museum
  • John Titor, time traveler from the future, looking for an IBM 5100?

  • Partial History of the IBM Computers

    • 1967: IBM builds the worlds first floppy disk.
    • 1967: IBM introduces the worlds first 8" floppy disk.
    • 1973: IBM introduces the IBM 3340 hard disk unit, known as the Winchester.
    • 1975: September - IBM's Entry Level Systems unit unveils "Project Mercury", the IBM 5100 Portable Computer.
    • 1981: September - IBM releases the IBM 5150 PC Personal Computer.
    • 1982: April - Eight months after the introduction of the IBM PC, 50,000 units have been sold.
    • 1982: May - Microsoft releases MS-DOS 1.1 to IBM, for the IBM PC.
    • 1982: June - The first IBM PC clone, the MPC, is released by Columbia Data Products.
    • 1982: August - After one year of production, IBM ships the 200,000th IBM PC.
    • 1982: November - Compaq Computer introduces the Compaq Portable PC, the first 100% IBM compatible. It cost Compaq US$1 million to create an IBM-compatible ROM BIOS that did not violate IBM's copyright.
    • 1982: At the West Coast Computer Faire, Davong Systems introduces its 5MB Winchester Disk Drive for the IBM PC, for US$2000.
    • 1983: March - IBM announces the IBM PC XT, with a 10 MB hard drive, 128KB RAM and a 360KB floppy drive. It costs US$5000.
    • 1983: November - IBM announces the IBM PCjr. It is US$700 for the bare configuration.
    • 1984: February - IBM introduces the IBM Portable PC.
    • 1984: March - IBM ships the IBM PCjr. It uses the 8088 CPU, 64KB RAM, and one 5.25-inch disk drive, but no monitor. It costs US$1300.
    • 1984: August - IBM announces the PC AT, for US$4000-6700.
    • 1985: April - IBM abandons production of the IBM PCjr.
    • 1986: April - IBM announces the IBM PC Convertible, 80C88-based, 256K RAM, and two 720K floppy disks, for US$2000.
    • 1986: April - IBM discontinues the IBM Portable PC.
    • 1986: September - IBM announces the IBM PC-XT Model 286, with 640KB RAM, 1.2MB floppy drive, 20MB hard drive, serial/parallel ports, and keyboard for US$4000.
    • 1987: IBM discontinues the IBM PC (model 5150) line.
      Source: Chronology of Events in the History of Microcomputers

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