Texas Instruments TI-99/4A advert


  • Type: Home computer
  • Manufacturer: Texas Instruments
  • Released: 1981
  • Discontinued: 1984
  • CPU: TMS9900 @ 3 MHz
  • Memory: 16 KB RAM (256 bytes scratchpad RAM)
  • Resolutions: bitmap mode 256×192, text mode 40 x 24 characters
  • Palette: 16 fixed colors (15 visible)
  • Audio: 3 voices, 1 noise (white or periodic)
  • Units shipped: ~2.8 million
  • Media: ROM cartridges and external cassette and floppy disk drives
  • Predecessor: TI-99/4

Released 1981: Texas Instruments TI-99/4A is a home computer released in June 1981 in the United States. It’s an enhanced version of the less successful TI-99/4 which was released in late 1979. The TI-99/4 and TI-99/4A are regarded as the first home computers using a 16-bit CPU, using the Texas Instruments TMS9900. However, the CPU performance is limited by the 8 bit hardware architecture of the rest of the machine. Both models include hardware support for sprites, using TI’s own chips, and multi-channel sound, making them some of the first home computers to include such custom chips, alongside the Atari 8-bit family also introduced in 1979.

The TI-99/4A remained mostly the same as its predecessor, with the major changes being a full-travel keyboard to replace the calculator-style keys, an improved graphics chip with support for bitmap modes, and a cleaner method of adding expansion cards. The price was also half of the original model. Texas Instruments supported the 4A with a line of peripherals, including a speech synthesizer, and a “Peripheral Expansion System” box to contain hardware add-ons.

While the TI-99/4A’s specifications look impressive on paper, architectural issues keep it from reaching the performance it appears capable of. The system failed to catch on with third party developers, with the majority of games and other software created and sold by TI. A price war with Commodore’s VIC-20 and Commodore 64 resulted in TI 99/4A prices dropping below 100 USD. Despite the increased user base created from selling large numbers of systems and peripherals at heavy discounts, after a 330 USD million loss in the third quarter of 1983, Texas Instruments announced the discontinuation of the TI-99/4A in October of 1983, and stopped production in March of 1984.

My TI-99/4A

When I bought it, the seller told me he had bicycled in poring rain from the city of Drammen to the city of Oslo here in Norway to buy this machine at discount from a shop back in the days, when he as a kid. This is around a 40 km ride each way with a lot of long up and downhills in each direction. I got the machine in the original box with the manuals and a Basic expansion cartridge. No storage media like a cassette recorder came along, but this computer can use any cassette recorder and even the audio output from an IPAD or laptop PC to load tape games.

Before I dared to power this machine on, I measured the voltage on the brick power supply. The outputs was a bit off and to high, but since its AC voltage and the power regulation circuits are located inside the machine itself and not in the brick supply, I took my chances, and the machine fired uo with no issues. The picture on my LCD flat screen was a bit “grainy”, but I think this is caused by the external RF modulator that connects to the antenna input of my LCD.

Texas Instruments TI-99/4A

Remi Jakobsen

I'm collecting classic computers and video games, stretching from the 70's into the 90's. Restoration, history, usage ...

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