Texas Instruments TI-99/4
Introduced:June 1979
Released:November 1979
Price: US$1,150 with monitor
CPU:TI TMS9900 @ 3MHz
Memory:16K RAM, 26K ROM
Display:Composite Video
RF modulator for TV display
32 X 24 text
192 X 256, 16 colors
Ports:ROM cartridge (on front)
Data storage cassette
Audio/Video output
Joystick input
CPU bus expansion
Peripherals:Speech Synthesizer
External 5-1/4" floppy drive
Thermal printer
Data storage cassette
RS-232 serial interface
OS:TI BASIC in ROM








For $1,150 you received the TI-99/4 console and one of the largest computer monitors ever released. The console has polished metal trim, giving it a quality appearance. The monitor is really a 13-inch Zenith color TV modified slightly to look and act like a computer monitor.

You had no choice - you had to purchase the monitor with the computer, as TI didn't have a legal RF modulator in which to use your own television set. Their planned RF modulator was not yet FCC approved.

The keyboard is more like a calculator than a real keyboard - known as "chiclet" style, difficult to type on because of the tiny keys. This is Texas Instrument's first computer. Before this, they made calculators, and it shows.


The TI-99/4 has the BASIC progamming language built-in. On boot-up, the user has the option of running TI-BASIC, an Equation Calculator, or the ROM cartridge, if one has been inserted.

Unfortunately, programs written in TI BASIC run ridiculously slow, because they are doubly-interpreted. First they are interpreted by the BASIC language, then they are interpreted again by TI's proprietary Graphics Programming Language (GPL).

Although a cassette tape drive was available, most commercial software programs were released on cartridges, which plug into the cartridge port on the front of the system.

Inside the cartridge, there are just a few ROM chips with the program already burned in. Shown here are the insides of the Yahtzee, Tunnels of Doom, and Mini Memory cartridges.

So far, we have over 80 unique cartidges in the collection. Always looking for more!


"Sidecar" expansion units can be attached to the system bus on the right side of the TI-99/4. These include:
Name/descriptionPart number Original price
Speech SynthesizerPHP1500$149.95
RS-232 ControllerPHP1700$224.95
Disk ControllerPHP1800$299.95
Disk Drive
  (needs PHP1800)		PHP1850$499.95
Thermal PrinterPHP1900$399.95
Memory Expansion (32K) PHP2200$399.95
Video ControllerPHP2300$699.95
P-Code Peripheral
  (needs 32K RAM)		PHP2400$399.95
Seen above is the TI-99/4 console with all of the Texas Instruments sidecars attached: Speech Synthesizer, Memory Expansion, RS-232 Serial Controller (with telephone modem), Video Controller, Disk Controller, Thermal Printer, and two floppy drives (attached to the Disk Controller).

Hope you have a wide desk to hold it all! The TI-99/4 can use a maximum of six sidecar peripherals, but the Speech Synthesizer must be first, and the Memory Expansion must be second.

The Memory Expansion unit does not have any connectors other than the system bus, but seen below are the rear-connections of the RS-232 (with two serial ports), the Disk Expansion, and the Video Controller.


The unusual Video Controller can act as an audio/video switcher, to direct either the computer video or an external audio/video signal to the monitor or other video device.
With an additional cable which plugs into the system bus on the right side of the Video Controller, it can save and load computer data to/from the VCR tape, control the VCR with commands such as STOP, REWIND, etc, or direct the VCR tape to a specific tape location.

The RS-232 sidecar is for serial communications with other peripherals, such as the TI-modem (left), which is used for telecommunications (dial-up) with other computers.

The Home Computer can send and receive messages, data, and entire programs through a standard telephone. It communicates with similarly equipped computers at remote locations, and accesses data bases and software services. So you can access stock prices, airline schedules, weather, restaurant menus, and shoppers guides. Uses the RS232 Interface and Terminal Emulator II.

The RF modulator (right) allows you to use your television instead of a computer monitor for the display.

Keyboard overlays (below) illustrate alternate key functions.





In February 1981, TI replaced the $450.00 Zenith monitor with a $399.95 Panasonic monitor. It has a smaller 10-inch screen instead of 13-inch.

Later that year, in June, TI replaced the TI-99/4 with the new and improved TI-99/4A. It has a better graphics chip and an improved keyboard.

Related Links

  • The TI99/4 Home Page from Andrew Gurudata's home page.
  • What Ever Happened to... The TI 9900 CPU?
  • TI-99/4A & Myarc Geneve Products
  • Rob Patton's page about the TI-99/4A
  • TI-99 Home Computer Web-Site
  • Bryan Roppolo's TI-99/4 site

    • 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, for an initial price of US$1500, including a color monitor.
    • 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.
    • 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



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