TX-0

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 magnetic core memory. The TX-0 was built in 1955 and went online in 1956 and was used continually through the 1960s at MIT. The transistorized TX-0 computer used 3600 transistors in its computer's circuitry and had also used the Philco high-frequency surface-barrier transistors in its design. In 1953, Philco had developed the world's first high frequency surface-barrier transistor, which was also the first transistor that was suitable for high speed computers. The TX-0 and its direct descendant, the original PDP-1, were platforms for pioneering computer research and the development of what would later be called computer "hacker" culture.

Designed at the MIT Lincoln Laboratory 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 Lab. 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 vector display system, consisting of a 12" oscilloscope with a working area of 7 by 7 inches connected to the 18-bit output register of the computer, allowing it to display points and vectors with a resolution up to 512×512 screen locations.

The TX-0 was an 18-bit computer with a 16-bit address range. First two bits of machine word designate instruction and remaining 16 bits are used to specify memory location or operand for special "operate" instruction. First two bits could create four possible instructions, which included store, add, and conditional 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 "add" instruction took 10 microseconds.

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