The TI-990 was a series of 16-bit minicomputers sold by Texas Instruments  (TI) in the 1970s and 1980s. The TI-990 was a replacement for TI's earlier minicomputer systems, the TI-960 and the TI-980. It had several uniquely innovative features, and was easier to program than its predecessors.

The TI-990 had a unique concept that registers are stored in memory and are referred to through a hard register called the Workspace Pointer. The concept behind the workspace is that main memory was based on the new semiconductor RAM chips that TI had developed and ran at the same speed as the CPU. This meant that it didn't matter if the "registers" were real registers in the CPU or represented in memory. When the Workspace Pointer is loaded with a memory address, that address is the origin of the "registers".

There are three hard registers in the 990; the Workspace Pointer (WP), the Program Counter (PC) and the Status register (ST). A context switch entailed the saving and restoring of only the hard registers. Programmers liked the TI-990 design because it had a fairly orthogonal instruction set which allowed a programmer to separately memorize all of the operations and the methods of accessing operands.

Our rack mount machine not only includes the main minicomputer system but is complete with the:
TI Omni 800 810 RO terminal printer - part no. 0994292-0001
TI Silent 700 ASR Electronic Data Terminal including the T33 ADSR Module - part no. 959389-0001
TI 911 VDT Video Terminal and keyboard.

All were very kindly donated by Richard and Diana Blanden.

Manufacturer: Texas Instruments
Date: 1975

This exhibit has a reference ID of CH11554. Please quote this reference ID in any communication with the Centre for Computing History.

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