UNIVAC Solid State
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The UNIVAC Solid State was a 2-address, bi-quinary coded decimal computer, with memory on a rotating drum with 5000 signed 10 digit words, spinning at 17,667 RPM in a helium atmosphere. It was announced by Sperry Rand in December 1958, as a response to the IBM 650. It came in two versions: the Solid State 80 (IBM-style 80 column cards) and the Solid State 90 (UNIVAC-style 90 column cards).
With 20 vacuum tubes, 700 transistors, and 3000 FERRACTOR amplifiers in its CPU, the Solid State was one of the first computers to use solid state components.
The system used a Clock that was recorded on a timing band on the main memory drum. This was read and amplified as a push-pull signal and processed through the main clock amplifier to the driver tubes that were 6146 series transmitter output tubes. The two 6146 tubes then fed the main clock power amplifier that consisted of two banks of three 4CX250 tubes running in parallel push-pull giving an output of about a kilowatt. The machine could be heard very clearly in the medium wave broadcast band and engineers used to listen to the clock running by using a standard radio as a monitor. The 4CX250's had B+ voltages of 1.5 kilovolts on their anodes and were quite lethal!
The line printer ran at 600 lines a minute and printing was initiated "on-the-fly". This means that the printable characters were distributed around a drum with letters, figures and punctuation marks being positioned at each column point and the drum made up of these elements was continuously rotating. As a particular element came up to the printing position (indicated by a timing arrangement on the end of the drum indicating a binary coded position to the main processor) a hydrogen thyratron would "fire" and cause an electro-magnet to call and present a small armature to the face of the printing paper with a ribbon similar to a typewriter ribbon interposed between the paper and the armature. As the armature was propelled forward onto the ribbon and the paper the character would be printed and immediately the armature would reset with a spring to await the next time the tube fired and the process would repeat on the next line down the sheet.
Timing was super critical throughout the operation of the card punch, the card reader and the printer, all being based on electromechanical principles. The card punch was made by de la Rue-Bull and was a mechanical nightmare to maintain.
