Texas Instruments Model 99/4A Personal Computer

When the TI-99/4a was introduced in 1981, Texas Instruments claimed it was both "a major breakthrough in computer technology," and, probably more important, the "lowest priced, 16-bit computer available." It cost only $525. The TI 99/4a was a redesign of the TI-99/4 system, which had been a market failure and was discontinued. The new machine sold well, but by August 1982, TI was falling behind its competitors, especially Commodore. So it began offering a $100 rebate on the TI-99/4a. It quickly became the best-selling home computer in America, controlling, by the end of 1982, approximately 35% of the market--150,000 machines a month.
In February 1983, TI cut the price to $150, and then in June 1983, it offered a plastic version of the TI-99/4a for less than $100. But now it had gone too far. It was selling computers for less than cost, resulting in a second quarter loss of $100 million.
The TI-99/4a operated on a TI TMS99000 at 3 MHz and included 16 KB of RAM and 26 KB of ROM. The computer included a RS-232 interface card and a 32K memory expansion card as well as a Data Storage cassette. Texas Instruments controlled the development of software for the machine and offered only around 300 titles. These did not include many of the most popular programs of the time.
Initially, the only way to expand the machine was to use a port on the right side of the console. Peripherals could extend out several feet. To remedy the situation TI released a more convenient Peripheral Expansion Box (PEB) and, surprisingly, sold 250,000 units at $1,475.00 each--far more than the cost of the computer.
Eventually Texas Instruments sold over 2.5 million units of the TI-99/4A. However the company decided that computers were not a promising business and dropped out of the PC market in 1984.
Currently not on view
Object Name
Date made
Texas Instruments
Physical Description
plastic (overall material)
metal (overall material)
average spatial: 5.7 cm x 3.81 cm x 2.6 cm; 2 1/4 in x 1 1/2 in x 1 in
ID Number
catalog number
accession number
Family & Social Life
Computers & Business Machines
See more items in
Medicine and Science: Computers
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Scott and Shane Briscoe

Visitor Comments

7/29/2015 11:19:02 AM
David C.
I remember this system when shopping for my first computer. It has good specs, but TI made it prohibitively expensive. In its normal configuration, you could only program it in BASIC (saving to cassette tape) or run ROM cartridge video games. In order to program it for real, you needed to buy the (very expensive) expansion chassis, a floppy drive, a P-code interpreter card, and a PASCAL compiler software package. For the amount of money involved, it was far cheaper and easier to buy a system from Apple, Commodore, Atari or Tandy. I ended up getting a TRS-80 Color Computer, which I used for many years, mostly running software I developed myself.
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