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TI99 4A



         


The Texas Instruments TI-99/4A was an early home computer, released in June 1981, originally at a price of $525. It was an enhanced version of the earlier TI-99/4, which had been released in late 1979 at a price of $1150. The TI-99/4A added an additional graphics mode and a full-travel keyboard (the 99/4 had a calculator-style chiclet keyboard).

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Features

In the TI-99/4A, the CPU, motherboard, and cartridge drive were built into a single unit with the keyboard. Available peripherals included a 5¼" floppy disk drive, an RS-232 interface, an in-line speech synthesizer module, and a 32 KB memory expansion card. Early models included a built-in equation calculator, but by 1984 this feature had been discontinued. In the early 1980s, TI was known as a pioneer in speech synthesis, and a plug-in speech module was available for the TI-99/4A.

The TI-99/4 series holds the distinction of being the first 16-bit personal computer. The TI-99/4A had a 16-bit TMS9900 CPU running at 3.3 MHz. However, the CPU chip was hampered by having only 256 CPU-addressable bytes in the machine's default configuration, and a 1-bit I/O bus, making it substantially slower than a true 16-bit microcomputer. The 16 bits were used to make speech synthesis possible, and could also be used by an experienced programmer to speed up some machine code programs.

Because the machine only had 256 bytes of RAM attached to the CPU, the TI99/4A's display coprocessor, a TMS9918, had its own RAM referred to as VDP RAM (visual display processor RAM). This memory was also used for storing the programs users wrote in the built-in BASIC programming language. Adding memory additional to the 16 KB of the videochip (16kb were needed for using graphics mode 2) was considered too expensive. Video memory was read/written by accessing a port, so the CPU's usual addressing mode could not be used. An interpreter (located in ROM, reachable by the CPU's usual addressing mode) was available to provide an instruction set on top of that mechanism. A side effect was that the TI-99's "native" instruction set was comfortable. The computer also had unusual features such as GROMs (graphic read-only memory) and an accompanying programming language called GPL (graphic programming language). As there was no realistic amount of RAM addressable by the CPU, machine code programs would not run unless more RAM was added in the form of either the 32 KB expansion card or the 4 KB mini memory module. Because of these, the TI-99 series gained a reputation for being quirky and eccentric, which endeared it to some and maddened others.

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History

Initially, the TI-99/4A was reasonably successful, and it has been estimated that it had about 35% of the home computer market at its peak. However, TI quickly found itself engaged in a price war, particularly with Commodore International, and was forced to lower the computer's price in order to compete. By August 1982, the computer was losing shelf space and TI offered a $100 rebate, which caused spokesman Bill Cosby to quip about how easy it was to sell a computer if you paid people $100 to buy one.

In February 1983, TI lowered the price to $150 and was selling the computers at a loss. And in June 1983, TI released a redesigned, cost-reduced version that it sold, also at a loss, for $99. TI lost $100 million in the second quarter of 1983 and $330 million in the third quarter. In October 1983, TI announced it was exiting the home computer business.

A total of 2.8 million units were shipped before the TI-99/4A was discontinued in March 1984.

The TI-99/4A was technologically a competitive computer, offering more memory and more advanced graphics capabilities than the Commodore VIC-20 and in some regards rivaling the Commodore 64, which was aimed at a higher point in the market. However, a number of elements of its design attracted criticism: All peripherals plugged directly into the right-hand side of the unit, which caused the computer to not fit well on top of a desk if a user added many peripherals besides a tape drive and a printer. In addition, the keyboard layout didn't match that of a typewriter very closely, which made it unpopular for word processing.

However, the 99/4A's biggest drawback was its limited software library. TI closely controlled software production for the machine, which resulted in a software library of around 300 titles and few of the big-name hits available for other computers of its day. By comparison, the VIC-20, whose history paralleled the TI-99/4 series except its software development was completely open, had a library of more than 700 titles.

As a result, the TI-99/4A found itself selling for around the same price as the VIC-20, even though it was much more expensive to manufacture.

The TI-99/4A maintained a cult following for years after its death in the marketplace, in part because of its eccentricities, and a number of PC-based emulators for it exist.

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Technical specifications

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