TX-0

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The TX-0, for Transistorized Experimental computer zero but affectionately referred to as tixo (pronounced "tix oh"), was an early fully transistorized computer and contained a then-huge 64K of 18-bit words of core memory. The TX-0 was built in 1955[1] and went online in 1956[2][3] and was used continually into the 1960s.

Contents

Background

Designed at the MIT Lincoln Laboratory[2] largely as an experiment in transistorized design and the construction of very large core memory systems, the TX-0 was essentially a transistorized version of the equally famous Whirlwind, also built at Lincoln Laboratory. While the Whirlwind filled an entire floor of a large building, TX-0 fit in a single reasonably sized room and yet was somewhat faster. Like the Whirlwind, the TX-0 was equipped with a display system, in this case a 12" oscilloscope hooked to output pins of the processor allowing it to display 512×512 points in a 7" by 7" array.

The TX-0 was a fully 16-bit computer with a 16-bit address range and 16-bit operations. Its word size was 18 bits; this allowed for 16 bits of data and 2 bits of instructions. These 2 bits could create four possible instructions, which included store, add, and branch instructions as a basic set. The fourth instruction, "operate", took additional operands and allowed access to a number of "micro-orders" which could be used separately or together to provide many other useful instructions. An addition took 10 microseconds.

Development

With the successful completion of the TX-0, work turned immediately to the much larger and far more complex TX-1. However this project soon ran into difficulties due to its complexity, and was redesigned into a smaller form that would eventually be delivered as the TX-2 in 1958. Since core memory was very expensive at the time, several parts of the TX-0 memory were cannibalized for the TX-2 project. After a time the TX-0 was no longer considered worth keeping, and was "loaned" (semi-permanently) to the MIT Research Laboratory of Electronics (RLE) in July 1958, where it became a centerpiece of what would eventually evolve into the MIT Artificial Intelligence Lab.

Delivered from Lincoln Laboratory with only 4K of core, the machine no longer needed 16 bits to represent a storage address. After about a year and a half the number of instruction bits were doubled to four, allowing a total of 16 instructions, and an index register was added. This dramatically improved programmability of the machine, but still left room for a later upgrade to 8K (the four instruction bits and one-bit indexing flag left 13 bits for addressing). This newly-expanded TX-0 was used to develop a huge number of advances in computing, including speech and handwriting recognition, as well as the tools needed to work on such projects, including text editors and debuggers.

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