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TI-99/ 4a

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The Texas Instruments TI-99/4A is a home computer released June 1981 in the United States at a price of US$525 (equivalent to $1,447 in 2018). It is an enhanced version of the less successful TI-99/4 model, which was released in late 1979 at a price of US$1,150 (equivalent to $3,970 in 2018). Both models include hardware support for sprites and multi-channel sound, some of the first home computers to include such custom co-processors, alongside the Atari 8-bit family also introduced in 1979. The TI-99/4 and TI-99/4A use the Texas Instruments TMS9900 16-bit processor, making them the first 16-bit home computers


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:

  • Disk controller card and one SS/SD floppy drive
  • RS-232 interface card
  • 32K memory expansion card

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 portSerial interface32K RAM expansionFloppy disk drive interfaceUnfortunately, CorComp filed for bankruptcy just a few months later, in August of 1984. 

  • By August 1982, TI is losing shelf-space to competitors, and issues a $100 rebate on the TI-99/4A.
  • At the end of 1982 the TI-99/4A is the number one home computer in America, with approximately 35% of the market share, and producing 150,000 consoles a month.
  • In February 1983, in order to remain competative, TI again cut the price to dealers, and the cost of a TI-99/4A dropped to about $150.
  • In June 1983, TI released the cheaper beige plastic version of the TI-99/4A, and again had to cut the price, to less than $100. They are now selling computers for less than it costs to manufacture them! As a result, TI experienced a second-quarter loss of $100 million.

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 80 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. 

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