Texas Instruments TI-99/4A
Released:June 1981
Price: US$525 (without monitor)
How many:2.8 Million
CPU:TI TMS9900, 3MHz
Memory:16K RAM, 26K ROM
Display:Video via an RF modulator
32 characters by 24 lines text
192 X 256, 16 color graphics
Ports:ROM cartridge (on front)
Data storage cassette
Audio/Video output
Joystick input
CPU bus expansion
Peripherals:Speech Synthesizer
Peripheral Expansion Box
Data storage cassette
300 baud modem
OS:ROM BASIC








The TI-99/4A is a redesign of the TI-99/4 system, which was discontinued. The new "4A" has a new graphics chip and a better keyboard.

About the only way to expand the original TI-99/4A was from the expansion port on the right side of the console. Memory expansion, a serial interface, a floppy drive and other peripherals can be plugged in here for added capabilities.

Unfortunately, this string of peripherals could easily reach many feet in length, as this picture of the original TI-99/4 indicates!

To remedy this situation, TI released the Peripheral Expansion Box as a more convenient way to expand the TI-99/4A. It is huge, and of very solid and high quality construction.

Introduced in January 1982, the Peripheral Expansion Box cost $1475.00, including: It is estimated that one PEB was sold (250,000) for every ten TI-99/4A consoles sold (2.5 million).





There is space inside the "PEB" for 8 cards, although one slot is required to contain the interface card which leads into the console via a very large flat cable.

The open PEB shown here has the interface card, an RS-232 Serial card, 32K RAM memory expansion, and floppy controller cards installed.


If the PEB is too large for you, CorComp, who manufactured many of their own expansion cards and peripherals for the TI-99/4A line of computers, released the CC-9900 Micro-Expansion System for the TI in May of 1984. It is a conveniently small expansion unit that plugs into the expansion bus on the right side of the 99/4A, and contains the same features as the PEB default configuration, and then some:
  • Parallel port
  • Serial interface
  • 32K RAM expansion
  • Floppy disk drive interface
    • Unfortunately, CorComp filed for bankruptcy just a few months later, in August of 1984.


    The new beige TI-99/4A has a re-designed and cheaper to build motherboard, as well as a cheaper, all plastic case. After the beige TI-99/4A was released, all new cartridges were also beige.
    So far, we have over 200 unique cartidges in the collection. Always looking for more!


    At about the same time, Milton Bradley announced the futuristic Milton Bradley Expansion System (MBX) for the TI-99/4A. It not only offered speech synthesis, but speech recognition, when used with specific Milton Bradley cartridges.

    After an initial voice training, the MBX system will recognize specific commands spoken into the microphone, as well as keyboard and joystick input.

    The joystick of the MBX is a 360 degree joystick - in addition to the usual up-down-left-right motion, it also rotates like the volume knob of your stereo.

    Unfortunately, in March 1984, shortly after the MBX became available, Texas Instruments decided that it could not compete in the home computer market, and discontinued the TI-99/4A. Thus, very few MBX systems were actually sold, and only about ten MBX specific game cartidges were ever produced.


    Back in January 1983, TI announced the TI-99/2 computer, to be sold for only $100.00. It had little in common with the 99/4A, the 99/2 was to be an inexpensive beginners computer like the Timex Sinclair 1000.

    Five months later, in June, they dropped plans to mass produce it, and it was never released. Strangely enough, there were advertisements and even articles published in computer magazines of the day.

    Read about the TI-99/2 in the June 1983 BYTE magazine article "A look at the design from concept to prototype".

    Related Links

  • TI-99/4A review from AtariMagazines.com
  • TI-99/4A & Myarc Geneve Products
  • 99er.net
  • TI-99 Home Computer Timeline - An historical account of the TI-99/4A

  • The Milton Bradley MBX Expansion System (robpatton.com)
  • "Getting Started With the Texas Instruments TI99/4A", by Stephen Shaw, 1983
  • MBX game controller from TI-99/4A Videogame House

  • TI-99 Cartridge Rarity List
  • Western Horizon Technologies TI 99/4a and Geneve Archive
  • Mainbyte's Home of the Texas Instruments Computers
  • Tunnels of Doom tribute page
  • TI99ers on-line user group

    • History of Texas Instruments' Computers

    • 1954: Texas Instruments produces the first commercial silicon transistor.
    • 1958: TI engineer Jack Kilby co-invents the integrated circuit.
    • 1964: Texas Instruments receives a patent on the integrated circuit.
    • 1967: TI develops the hand-held calculator.
    • 1971: TI develops the first microcomputer-on-a-chip, containing over 15,000 transistors.
    • 1976: June - Texas Instruments introduces the TMS9900, the first 16-bit microprocessor
    • 1979: June - TI introduces the TI-99/4 personal computer.
    • 1979: November - TI begins shipping the TI-99/4.
    • 1980: January - Production problems haunt TI-99/4 for the first few months of 1980 and TI is selling fewer than 1000 units per month.
    • 1980: TI introduces a 5 1/4-inch mini-floppy disk drive for the TI-99/4. It can store up to 90KB per disk. Price for controller is US$300; price for disk drive is US$500.
    • 1980: TI introduces a 300 baud modem for the TI-99/4 for US$225.
    • 1980: TI introduces a thermal printer for the TI-99/4. It produces 5x7 dot matrix characters, at 30 CPS, on 3 1/2-inch thermal paper. Price is US$400.
    • 1980: TI introduces an RS-232 interface for the TI-99/4. Price is US$225.
    • 1981: June - The new and improved TI-99/4A Home Computer is unveiled for $525.
    • 1982: January - TI introduces a Peripheral Expansion Box for the TI-99/4A for $250. Expansion cards are approximately $300 - $500 each.
    • 1982: February- Unsatisfied at Texas Instruments, three engineers (Rod Canion, Jim Harris, Bill Murto) leave and form Compaq Computers, to build the world's first true IBM clone, the Compaq Portable. It was an incredible success.
    • 1982: June - TI hires Bill Cosby as the ad campaign spokesman for their Home Computer. It costs TI $1 million a year.
    • 1983: January - TI announces the TI-99/2.
    • 1983: March - Texas Instruments introduces the Compact Computer 40 (CC-40). It runs on four AA batteries, lasting up to 200 hours.
    • 1983: June - TI drops plans to market the TI-99/2.
    • 1983: June - TI releases the plastic beige console version of the TI-99/4A.
    • 1983: July - TI ships the 1 millionth TI-99/4A.
    • 1984: January - TI has sold 2.5 million TI-99/4As.
    • 1984: March - TI gives-up and drops-out of the home computer market altogether.
      Source: Chronology of Events in the History of Microcomputers
      and
      TI-99 Home Computer Timeline by Bill Gaskill






    Return to the Obsolete Technology Homepage